JP2001082454A - Hydraulic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable rotation leaving a core shaft static even at a high speed, supply lubrication fluid with ease and use for a long time. SOLUTION: This hydraulic bearing is provided with a radial hydraulic bearing section R between a shaft 11 and a sleeve 12 opposing to the shaft 11 through a bearing clearance. Along with the relative rotation of the shaft 11 and the sleeve 12, pressure is generated in the lubrication fluid in the radial hydraulic bearing section R. In this case, the clearance between at least a part of a shaft external peripheral surface 11g and a sleeve internal peripheral surface 12n is made unequal. A small section Cmin of the clearance is arranged nearly symmetrical about the shaft center, made nearly the same as a radial clearance Rc and communicated with the radial clearance Rc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a fluid bearing for video equipment, and more particularly to an improvement of a fluid bearing which is optimal for a magnetic disk device (HDD), an optical disk device and the like.

[0002]

2. Description of the Related Art A conventional fluid bearing of this type is disclosed, for example, in FIG.
(A) and (b) are known. This conventional fluid bearing is provided with two radial fluid bearings R, R between a shaft 1 and a sleeve 2 cooperating with the shaft 1, and these two fluid bearings R, R The cylindrical outer peripheral surface 1g of the pinched shaft 1 and the cylindrical inner peripheral surface 2n of the sleeve 2 are mutually eccentric. A reservoir 3 for holding a lubricating fluid such as oil or grease is formed in a narrow portion C _S of the clearance between the two cylindrical walls.
_H has a ventilation hole 4 opened. As described above, the small clearance portion C formed by eccentrically arranging the two cylindrical walls 1g and 2n.
By giving _S the function of a reservoir as a lubricating fluid reservoir, long-term use of fluid bearings is addressed.

[0003] A small clearance C as a reservoir
The size of the clearance of _S changes in the taper shape in the axial direction in the vicinity of the radial fluid bearing R similarly to the wide portion C _{H of the} clearance, and communicates with the radial fluid bearing R while gradually narrowing. On the other hand, an air chamber is formed by the portion C _H having a large clearance, and the ventilation hole 4 opened therethrough is communicated with the outside air to promote separation and discharge of air bubbles remaining in the lubricating fluid. As a result, changes in the ambient temperature during use of the fluid bearing,
Alternatively, the lubricating fluid is prevented from being pushed out to the outside by the expansion of the air in the bearing caused by a change in the outside air pressure when the fluid bearing is transported by aircraft.

[0004]

However, in such a conventional eccentric fluid bearing, the outer peripheral surface 1g of the shaft and the inner peripheral surface 1n of the sleeve are mutually eccentric and are not rotationally symmetric. Therefore, as a result of the wedging action of the lubricating fluid is fed to the narrow portion C _S clearance becomes high-speed rotation becomes stronger, have opposite directions (that is, the direction of the air chamber C _H) shortcomings axis to the slightly moving the narrow gap It has been found.

That is, although there is no problem for use at low speed, in recent years, HDDs equipped with fluid bearings have been used.
The speeding up of such devices is becoming remarkable, and accordingly, the hydrodynamic bearing itself tends to be used at a high speed. A phenomenon in which the shaft center moves slightly due to the increase in the rotation speed and the rotation becomes unstable becomes apparent for the first time, and measures and improvements are required.

[0006] In the case of a conventional eccentric fluid bearing, the operation of filling a lubricating fluid into two axially separated radial fluid bearings R, R is performed by supplying oil from an intermediate portion between the two bearings R, R, or Either the two bearings R, R were separately lubricated. This is very inconvenient in the work of assembling the eccentric fluid bearing. Therefore, the present invention has been made by focusing on the unsolved problems of such conventional eccentric fluid bearings, whereby stable rotation can be obtained without moving the shaft center even at high speed rotation, and supply of lubricating fluid is also achieved. An object of the present invention is to provide a fluid bearing which is easy and can be used for a long time.

[0007]

In order to achieve the above object, the present invention according to claim 1 comprises a radial fluid bearing between a shaft and a sleeve opposed to the shaft via a bearing clearance. In a fluid bearing that generates pressure in the lubricating fluid of the fluid bearing portion in accordance with relative rotation between the shaft and the sleeve, at least a portion of the shaft outer peripheral surface and the sleeve inner peripheral surface at locations other than the radial fluid bearing portion. The size of the clearance is made non-uniform in the circumferential direction, and the portion with the small clearance is made to be approximately the same size as the radial bearing clearance, communicated with the radial bearing clearance, and arranged almost rotationally symmetric with respect to the axis. Features.

According to the present invention, the smaller one of the clearances between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, which functions as a reservoir for holding the lubricating fluid, is substantially rotated with respect to the axis. Due to the symmetrical arrangement, even if the wedge action of the lubricating fluid sent to the reservoir at high speed rotation becomes stronger, they cancel each other out at the symmetrical position. Therefore, there is no movement of the shaft center, and stable rotation is ensured.

Here, in the fluid bearing according to the first aspect of the present invention, the smaller clearance portion has a size substantially equal to the radial bearing clearance over the entire axial direction between the radial fluid bearing portions, so that both radial bearings have the same size. It can be made to communicate with the bearing clearance. With this configuration, when the radial fluid bearings are provided at both ends, when the lubricating fluid is injected into one of the bearings, the other bearing is simultaneously filled with the lubricating fluid through the smaller clearance.

In addition, the taper surface which gradually narrows the clearance between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve at a portion other than the radial fluid bearing portion is gradually reduced toward the radial fluid bearing portion. And the angle formed by the tapered surface with the axis is 30 ° or less, and the tapered surface communicates with the radial fluid bearing portion. In this case, the lubricating fluid held in the smaller clearance can be reliably supplied to the radial fluid bearing portion by utilizing the surface tension.

The air chamber may be provided in a portion having a large clearance between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, and the air chamber may be provided with a vent hole communicating with the outside air. In this way, by opening the ventilation holes communicating with the outside air in the air chamber, the separation and discharge of the lubricating fluid held in the reservoir portion and the air bubbles remaining in the bearing internal space sandwiched between the plurality of fluid bearings and the cylindrical wall are prevented. Easy to do.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a fluid bearing of the present invention, FIG. 2 is a sectional view of a side surface thereof, and FIGS. 3 (a) to 3 (d) are sectional views taken along line III-III of FIG. First, the structure will be described. This fluid bearing is a type used for shaft rotation. A sleeve 12 for supporting a rotating shaft 11 has radial fluid bearing portions R, R at both axial ends of an inner peripheral surface 12n thereof. It has. This radial fluid bearing part R,
A groove M for generating dynamic pressure is provided on the cylindrical inner peripheral surface of R. The illustrated groove pattern has an asymmetric herringbone shape in which the outer groove is longer than the inner groove, and is effective for supplying the lubricating fluid to the inner side of the sleeve with the rotation of the shaft 11 and preventing scattering to the outside. It is.

The sleeve 12 excluding the fluid bearing portions R, R
The inner peripheral surface 12n has a sectional shape shown in FIGS.
As shown in FIG. The minor axis of the ellipse in each section is the same as the diameter of the cylindrical inner peripheral surface of the radial fluid bearings R, R. On the other hand, the cross-sectional shape of the outer peripheral surface 11g of the shaft 11, which is the mating member, is circular. Therefore, the clearance between the two members 11, 12 changes in the circumferential direction,
Its size is not uniform. The portion C _min where the size of the clearance is the smallest in each cross section is located at the minor diameter portion of the ellipse, and there are two portions almost rotationally symmetric with respect to the axis. Each of them has a size substantially equal to the bearing clearance Rc of the radial fluid bearing R over the entire length in the axial direction of a portion sandwiched between the radial fluid bearings R, R at both ends, and communicates with the bearing clearance Rc.

The portion C _max where the size of the clearance is largest for each cross section is also arranged substantially rotationally symmetric with respect to the axis. Further, the elliptic ratio of the elliptical cross section of the inner circumferential surface 12n of the sleeve is determined by changing the radial distance between both ends of the sleeve so that the clearance between the two members 11, 12 changes in the circumferential direction and at the same time in the axial direction. The diameter of the fluid bearings R, R is gradually increased from the end to the center of the sleeve. That is, the radial fluid bearing R extends from the elliptical cylindrical portion (see FIG. 3C) in the cross section IIIc at the center of the sleeve 12.
3 (b), the inner circumferential surface 12n of the sleeve reaching the portion.
By gradually changing the elliptical ratio as shown in FIG. 7A, a tapered surface 12t in which the clearance between the shaft 11 and the radial bearing clearance Rc gradually narrows is partially formed,
The end of the tapered portion communicates with the radial fluid bearing R (see FIG. 2). The angle α between the tapered surface 12t and the axis is preferably designed to be 30 ° or less, whereby the bearing clearance R of the radial fluid bearing R due to surface tension is reduced.
The supply of the lubricating fluid to c is reliably performed.

An inner peripheral surface 12n of the sleeve 12 having an elliptical cross section.
The portion C _max where the size of the clearance between the shaft 11 and the circular outer peripheral surface 11g is the largest for each cross section is located at the major diameter portion of the ellipse, and a vent hole 14 communicating with the outside air is opened in that portion. ing. Next, the operation will be described. In order to assemble and fill the lubricating fluid with the fluid bearing configured as described above, the lubricating fluid may be injected into one of the radial fluid bearings R from outside the sleeve 12. Then, the supplied lubricating fluid through the clearance small portion C _min between the axis outer peripheral surface 11g of the sleeve inner circumferential surface 12n having substantially equal size as the radial bearing gap Rc, the radial fluid bearing R on the other side Is also supplied. Therefore, the operation of filling the fluid bearing of the present invention with the lubricating fluid is extremely easy.

By driving a device equipped with this fluid bearing,
When the shaft 11 is rotated, the dynamic pressure generating groove M is rotated during the rotation.
, A dynamic pressure is generated in the lubricating fluid in the portion of the radial fluid bearing R, and the shaft 11 is supported in a non-contact manner in the radial direction. On the other hand, in the portion between the radial fluid bearings R, R at both ends of the sleeve 12, lubrication is performed to a portion C _min where the clearance between the inner peripheral surface 12n of the elliptical cross section and the outer peripheral surface 11g of the circular cross section is the smallest. The reservoir is formed by holding the lubricating fluid by the surface tension and wedge action of the fluid. As the rotation speed of the shaft 11 increases, the wedge action in the reservoir portion is promoted, and the reaction force increases. However, in the case of the present invention, minimum clearance portion C _min that functions as a reservoir, since mutually 180 ° phase is formed in a different rotational symmetry, will be balanced by the reaction force between,
No movement of the shaft 11 occurs. Therefore, stable rotation can be obtained.

The _Cmax portion having a large clearance between the inner peripheral surface 12n of the sleeve and the outer peripheral surface 11g having a circular cross section functions as an air chamber, and air remaining in the air inside the fluid bearing or the lubricating fluid is removed from the shaft 11 Is collected there with the rotation of and is discharged to the outside air through the ventilation holes 14. The lubricating fluid from which the air has been removed and which is retained in the reservoir and its vicinity is
1 is guided to the tapered surface 12t which gradually narrows toward the radial fluid bearing R, and is reliably supplied to the radial fluid bearings R, R by the action of surface tension.

Thus, according to the fluid bearing of the present invention, lubrication of lubricating fluid to the radial fluid bearing portions R, R at both ends is achieved by:
The fluid bearing can be easily operated from the outside without disassembling the bearing, and the lubricating fluid held in the reservoir can be reliably supplied to the radial fluid bearing R, so that long-term operation is possible. In the above-described embodiment, the description has been given of the shaft rotation type fluid bearing. However, the present invention can be applied to a sleeve rotation type fluid bearing.
In this case, however, the axis on the stationary side is made elliptical instead of making the sleeve elliptical.

In the case where the bearing span is short and the space surrounded by the plurality of radial fluid bearings and the cylindrical wall is narrowed, so that the residual air bubbles are small and the use environment is not severe, the ventilation opening to the air chamber is required. Holes can be omitted. When the ventilation hole is not provided as described above, not only the stationary side but also the rotating side may have an elliptical cross section. Further, the cross-sectional shape of the shaft or sleeve constituting the fluid bearing of the present invention is not necessarily limited to a pseudo-elliptical shape such as an elliptical shape or an oval shape, and the clearance changes in the circumferential direction. If so, a triangular arc having reservoirs at 120 ° intervals or a polygonal shape having other reservoirs at equal intervals may be used.

The number of fluid bearings is not limited to two, and a reservoir may be provided adjacent to one fluid bearing, or a reservoir may be provided between a plurality of bearings of three or more fluid bearings.

[0021]

As described above, according to the first aspect of the present invention, the clearance between the shaft and the sleeve in the vicinity of the fluid bearing portion is made non-uniform in the circumferential direction, and the lubricating fluid holding / supplying source is Since a portion having a small clearance functioning as a reservoir is provided in a rotationally symmetric manner, the axial center does not move even if the number of rotations is increased, and as a result, there is an effect that stable rotation can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view of an embodiment of a fluid bearing according to the present invention.

FIG. 2 is a side sectional view of FIG.

3A is a sectional view taken along line IIIa-IIIa in FIG. 2,
2B is a cross-sectional view taken along the line IIIb-IIIb in FIG. 2, and FIG.
FIG. 3D is a sectional view taken along the line III c-III c, and FIG.
It is an Id line sectional view.

4A and 4B show a conventional fluid bearing, in which FIG.
(B) is the bb line sectional view.

[Explanation of symbols]

1 shaft 11 shaft 2 sleeve 12 sleeve R Radial fluid bearing Rc Radial fluid bearing clearance C _min Small clearance

Continuation of the front page (72) Inventor Ikuki Sakatani 1-5-150 Kugenuma Shinmei, Fujisawa-shi, Kanagawa F-term in NSK Ltd. (reference) 3J011 AA04 BA02 CA01 CA02 CA04

Claims (1)

[Claims] 1. A radial fluid bearing portion is provided between a shaft and a sleeve opposed to the shaft via a bearing clearance, and a pressure is generated in a lubricating fluid of the fluid bearing portion as the shaft and the sleeve rotate relative to each other. In the fluid bearing, the size of the clearance between at least a part of the shaft outer peripheral surface and the sleeve inner peripheral surface in a portion other than the radial fluid bearing portion is made non-uniform in the circumferential direction, and the small clearance portion is
A fluid bearing having a size substantially equal to the radial bearing clearance, communicating with the radial bearing clearance, and being arranged substantially rotationally symmetric with respect to an axis.