JPH0328517A - Dynamic pressure bearing unit - Google Patents

Abstract

PURPOSE:To make the load capacity of the unit in the title larger, compact in its size, and also prevent pollution by oil mist thereby,by constituting an unit in which grooves for dynamic pressure generation for radial and thrust bearings are provided and gas is contained in the radial bearing clearance and lubricant is contained in the thrust bearing clearance. CONSTITUTION:A radial bearing R having small unit load capacity but having a gas lubricating type groove 33 generating dynamic pressure free from production of environmental contaminants provided in the outside diameter side of a large-diameter cylindrical fixed member 21 so that sufficient load capacity may be provided. On the other hand, a thrust bearing S of large unit load capacity and compact size having a lubricant lubricating type dynamic pressure generating groove 26 is provided at the center of the fixed member 21, this bearing unit is made compact. Oil mist produced on the thrust bearing S by the rotation of a rotating member 30 can be effectively prevented from being spattered outwards by the pressurized gas from the radial bearing R.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to drive devices for magnetic disks, magneto-optical disks, etc., VTRs (video tape recorders), LBs, etc.
This invention relates to a hydrodynamic bearing device used in P (laser beam printer), DA'r (digital audio table recorder), etc.

[Conventional technology]

As a conventional hydrodynamic bearing device of this kind, there is one shown in FIG. 5, for example. This prior art is a hydrodynamic bearing device for a rotational drive device for a magnetic disk D, and a housing l, which is a fixed member, has a cylindrical sleeve IA at its center, and a cylindrical hole 2 at the axis of the sleeve IA. are doing.

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, thereby forming a radial support R.

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 sliding shaft 5 facing the thrust bearing surface 9 .

A groove 11 for generating dynamic pressure is formed in at least one of the thrust bearing surface 9 and the thrust bearing surface 10, thereby forming a thrust bearing S.

A motor stator 12 is attached to the outer diameter surface of the cylindrical sleeve IA of the housing l, and the motor stator I2 is attached to the inner diameter surface of a hub (rotating body) 13 that is integrally fixed to the upper end of the shaft 5. A motor rotor l4 is mounted opposite to the motor rotor l4.

Bearing clearance l5 of radial bearing R and thrust bearing S
The bearing clearance 16 is filled with lubricating oil or grease as a lubricant.

When the motor stator l2 is energized, the motor rotor 14 rotates together with the hub 13 and shaft 5.

Due to the bombing action of the grooves 7 and 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 in the semi-longitudinal direction and the vertical direction. Supported by

[Problems to be Solved by the Invention] In the above-mentioned conventional hydrodynamic bearing device that uses lubricant in the radial bearing R and the thrust bearing S, there is a problem in that “the oil mist is scattered to the outside due to the rotation of the sleeve 5”. It is necessary to prevent the magnetic disk D from becoming contaminated as much as possible.

ξ7However, it is very difficult to completely block the external scattering of oil mist.

In the end, the problem of oil mist contamination can be solved by using gas lubrication as a whole, but in that case, the viscosity of gas is extremely small compared to oil, etc., so the load on the bearing is small, or the bearing is This is limited to cases where the size is large and the °C is good. In other words, in the past, there was a problem in that it was not possible to realize a compact hydrodynamic bearing device that could be used in a relatively large load range without fear of contamination by oil mist. The present invention has been made in view of these conventional problems, and its purpose is to provide a hydrodynamic bearing device that has a large load capacity, is compact, and does not cause contamination due to oil stroke. It's about doing.

(Means for Solving the Problems) The fixed member has a cylindrical radial bearing surface provided on the outer diameter surface and a thrust bearing surface provided at a distance radially inward from the radial bearing surface. The rotating member that fits into the fixed 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 the thrust bearing clearance 7 in between. At least one of the radial bearing surface and the radial bearing surface is provided with a groove for generating dynamic pressure for the radial bearing, and at least one of the thrust bearing surface and the thrust bearing surface is provided with a groove for generating dynamic pressure for the thrust bearing. Gas is present in the radial bearing clearance, and lubricant is present in the thrust bearing clearance.

[Effect]

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 fixing member with a large diameter, so that the bearing has sufficient capacity. It can be a load capacity. On the other hand, the fixed member is provided with a thrust bearing having a groove for generating dynamic pressure using lubricant, which has a large unit load capacity and can be made compact, in the center of the fixing member.

In addition, the pressure gas of the radial bearing effectively prevents oil mist generated in the thrust bearing due to the rotation of the rotating member from scattering to the outside.

In this way, a compact, high-load, pollution-free hydrodynamic bearing device can be provided.

[Embodiment] FIG. 1 is a longitudinal cross-sectional view of a first embodiment of the present invention, and a second view is a plan view of its thrust bearing surface. In this embodiment, the hydrodynamic bearing device of the present invention is applied to a magnetic disk drive (HDD). A large diameter cylindrical sleeve 2l, which is a fixed member, is integrally attached to the base 20. On the outer diameter surface of the sleeve 2l, there are two points spaced apart in the axial direction.
A cylindrical radial bearing surface 22 is provided. Further, a through hole 23 is formed at a position spaced ni1 inward from this radial bearing surface 22 in the radial direction, that is, at the axial center of the sleeve 21, and a cylindrical thrust receiver 24 is formed at the lower end of this through hole 23.
is fixed by means such as press-fitting.

The flat upper end surface of the thrust receiver 24 serves as a thrust bearing surface 25, on which a spiral groove 26 for generating dynamic pressure is formed as shown in FIG.

A face-down cup-shaped hub 28 is aligned with the sleeve 2l, which is the fixing member. One end of a shaft 29 is press-fitted into the center of the hub 28, and the shaft 29 is attached to the sleeve 21.
It is loosely inserted into the through hole 23 of , with a gap 27 in between. The hub 28 and the shaft 29 constitute a rotating member 30.

The inner diameter surface of the hub 28 is a radial bearing surface 32 that faces the radial bearing surface 22 through a radial bearing clearance 31, and this radial bearing surface 32 is provided with a herringbone-shaped groove 33 for generating dynamic pressure. . The radial bearing surface 32 and the radial bearing surface 22 constitute a dynamic pressure type radial bearing R. Gas (air in this case) exists in the radial bearing clearance 31, and gas lubrication is provided.

On the other hand, the free end of the shaft 29 is connected to a thrust bearing surface 3 which is opposed to the thrust bearing surface 25 through a thrust bearing clearance 35.
It is said to be 6. Thrust bearing surface 25 and thrust bearing surface 3
6 and motion J. E-type thrust 1 and bearing S are constructed.

The clearance 4 method δr of the radial bearing clearance 31 is the shaft 29
The gap dimension δ of the clearance 27 between the inner diameter surface 23A of the sleeve (that is, the inner diameter of the through hole 23) is smaller than 7, and the radial bearing surface 32, which is the inner surface of the hub, is not interfered with by the shaft 29. It is guided to a radial bearing 22 which is the outer diameter of the sleeve.

Thrust bearing gap 35 on inner diameter surface 23A of sleeve 21
The vicinity of the sleeve 23A has a larger diameter than other parts of the sleeve inner diameter surface 23A, and is provided with a cucumber reservoir 40 in which a lubricant 39 such as lubricating oil or grease is stored. The capacity of this oil reservoir 40 is determined by the thrust bearing clearance 3 during rotation of the rotating member 30.
5, the amount of lubricating oil is made sufficiently larger than that required to form a lubricating oil film.

A motor stator 41 is attached to the upper surface of the base 20 near the base of the sleeve 21, and a motor rotor 42 is attached to the lower end surface of the hub 28 so as to face the motor stake 4l in plan view.

One or more magnetic disks D are mounted on the outer diameter surface 28A of the hub 28 of the hydrodynamic bearing device configured as described above via the mounting member 43.

Next, the action will be explained.

When the coil of the motor stator 41 is energized, rotational force is generated in the motor rotor 42. As a result, the rotating member 30 consisting of the hub 28 and the shaft 29 rotates together with the magnetic disk D. Due to this rotation, dynamic pressure is generated in a herringbone-shaped dynamic pressure generating ring 33 formed on the radial receiving surface 32, which is the inner diameter surface of the hub 28. Therefore, the hub 28 is supported in the radial direction by the pressure of the air within the radial bearing clearance 31 while maintaining non-contact with the sleeve 21.

In this case, the inner diameter of the hub 28 that holds the radial bearing R is large, and the bearing effective diameter is large. Therefore, despite gas lubrication, a sufficient radial fi load capacity is obtained.

In addition, in a magnetic disk drive device, the magnetic disk D
It is necessary to ensure coaxiality between the outer diameter surface 28A of the hub 28 to which the radial bearing R is attached and the inner diameter surface of the hub 28 that holds the radial bearing R with high precision. Regarding this point, since it is the inner and outer surfaces of the hub 28, it can be easily machined with high precision.
It is possible to reduce the fluctuation of the rotational speed component, and
An effect has been obtained in that it can be suppressed to 11 times as small as possible.

In the thrust bearing S, the "re-rotation" of the shaft 29 and the
Dynamic pressure is generated by the spiral groove 26 for dynamic pressure generation L formed in the thrust bearing surface 25 of the thrust receiver 24. Therefore, the shaft 29 floats to the side 1ii1 due to the pressure of the lubricant 39 in the thrust bearing clearance 35, and is supported while maintaining contact with the thrust receiver 24.

In this case, the thrust bearing S is lubricated using a lubricant or grease, so that a large axial load capacity is obtained even though it is compact.

It is also possible to add a grounding effect by using as the lubricant 39 an electrically conductive lubricant containing a conductive lubricant such as carbon or metal.

Further, this thrust bearing S has a raffle 40 having a capacity sufficiently larger than the amount of lubricant required to form a required lubricant film on the thrust 1 and the bearing gap 35. As a result, the lubricant 39 of the thrust bearing S overflows from the gap 27 between the shaft 29 and the sleeve inner surface 23A and reaches the radial bearing R, resulting in a situation where the torque of the radial bearing R increases significantly. It has the effect of reducing fat.

Furthermore, even if the lubricant 39 does not overflow directly from the thrust bearing S, it is inevitable that oil error will occur during shaft rotation, and this will pass through the clearance 27 of the shaft 29 and the radial bearing clearance 31. When released outside the hub 2B,
The magnetic disk D becomes contaminated. However, in this embodiment, since the radial bearing R is lubricated with gas, the gas whose pressure is increased as the hub 28 rotates within the radial bearing clearance 31 traps oil mist within the hub 28.

Therefore, the cleanliness of the outside of the magnetic disk D and the hub 28 can be ensured.

FIG. 3 shows a second embodiment of the invention.

This embodiment differs from the first embodiment in the structure of the thrust bearing S and the mounting of the drive motor.

That is, a recess 52 is formed at the center of the upper surface of the sleeve 5l instead of the through hole 23, and the bottom surface 53 of the recess 52 is used as the thrust bearing surface 25. On the other hand, the 'F end surface of the short shaft 54 fixed to the center of the hub 28 serves as the thrust receiving surface 36,
A spiral groove 26 in the river that generates dynamic pressure is formed. −
The upper lubricant 39 is stored in the L recess 52 . When grease is used as the lubricant 39, since the grease has a high viscosity, it can also be used in an upside down state as shown in the figure.

A motor stator 55 is attached to the inner circumferential surface of the stepped portion of the base 20, and a motor rotor 56 is attached to the lower end side surface of the hub 28 so as to be circumferentially opposed to the motor stator 55.

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

The fourth layer 1 shows the third embodiment.

In this embodiment, the motor rotor 62 is connected to the motor stake 63.
It is arranged inside the radial bearing R. However, the shaft 60 is erected and fixed on the base 20, and the base 20 and the shaft 60 constitute a fixed member. An inner sleeve 61 surrounding the shaft 60 is rotatably fixed to the hub 28, and the hub 28 and sleeve 61 constitute a rotating member. A groove 26 for generating dynamic pressure is formed in the thrust bearing surface 25 of the upper end surface of the shaft 60, and the thrust bearing surface 3
6 and is opposed to the bottom surface of the inner sleeve 6■.

This thrust bearing S is lubricated with lubricant.

A cylindrical motor rotor 62 is attached to the outer diameter surface 61A of the inner sleeve 61. A motor-less stator 63 disposed circumferentially on the outside of the motor rotor 62 is fixed to an inner periphery 64A of an outer sleeve 64 that projects upwardly from the base 20 in a cylindrical shape. In this embodiment, the motor stator 62 and the motor stator 63 are circumferentially opposed to each other, but they are not necessarily circumferentially opposed to each other, and may be motors that are planely opposed to each other.

A radial bearing surface 22 is formed on the outer diameter surface of this outer sleeve 64.
The inner diameter surface of the hub 28 facing this is a radial receiving surface 32, and a radial receiving surface 32 for generating dynamic pressure is formed. This radial bearing R is gas-lubricated.

By placing the drive motor inside the radial bearing R, there is the advantage that a more compact device can be obtained.

In each of the above embodiments, the groove pattern of the groove 33 for generating dynamic pressure of the radial bearing R was a dogleg-shaped ring-bone groove. However, in addition to this, a figure-eight herringbone groove or even a spiral {M} groove may be used.

Moreover, although the grooves 33 for generating dynamic pressure are formed in two rows with an interval in the axial direction, they may be formed in one row.

Further, the groove 33 for generating dynamic pressure for the radial bearing may be provided on either the radial bearing surface 22 or the radial receiver 32, or may be provided on both.

Similarly, the groove 26 for generating dynamic pressure for the thrust bearing may be provided on either the thrust bearing surface 25 or the thrust receiving surface 36, or may be provided on both.

[Results of invention]

As explained above, according to the present invention, a radial bearing, which has a small unit load capacity but has no risk of generating environmental pollutants, can be used in a cylindrical bearing with a large diameter. A thrust bearing is provided on the outer diameter side of the fixed member, and a thrust bearing is provided in the center of the fixed member to drive a groove for generating dynamic force using a lubricant lubrication method that has a large unit load capacity and can be made compact. Therefore, radial bearings. Both thrust bearings have sufficient load capacity and can effectively prevent lubricant from scattering to the outside, making it compact and capable of high loads. We can provide pollution-free hydrodynamic bearing devices.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention, FIG. 2 is a plan view of its thrust bearing surface, FIG. 3 is a longitudinal sectional view of a second embodiment of the invention, and FIG. 4 is a longitudinal sectional view of the second embodiment of the present invention. A vertical cross-sectional view of the third embodiment of
FIG. 5 is a longitudinal sectional view of a conventional hydrodynamic bearing device. 2+, 51.64 is a sleeve (fixing member), 22 is a radial bearing surface, 24 is a thrust receiver, 25 is a thrust bearing surface, 26 is a groove for generating dynamic pressure, 30 is a rotating member, 3l is a radial bearing clearance, 32 3 is a radial bearing surface, 33 is a groove for generating dynamic pressure, 35 is a thrust bearing clearance, 36 is a thrust bearing surface, and 39 is a lubricant.

Claims (1)

[Claims] (1) The fixed member has a cylindrical radial bearing surface provided on the outer diameter surface and a thrust bearing surface provided at a distance radially inward from the radial bearing surface, and the fixed member rotates to fit into the fixed member. The 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, and at least one of the radial bearing surface and the radial bearing surface. is provided with a groove for generating dynamic pressure for the radial bearing, a groove for generating dynamic pressure for the thrust bearing is provided on at least one of the thrust bearing surface and the thrust bearing surface, and gas is present in the radial bearing clearance; A hydrodynamic bearing device in which a lubricant exists in the thrust bearing clearance.