DE102005005414B3 - Fluid-dynamic bearing system for rotary bearing of spindle motor used in hard disk drive assembly, has bushings surrounding divided sections of tubular case surrounding rotary shaft, forming gap which is filled with bearing fluid - Google Patents

Abstract

The system includes a shaft (2) that is surrounded by a tubular case (4), and that rotates around a rotation axis (3). A flange (9) is formed at the outer circumference of the case to divide the case into upper and lower sections (4a,4b). The upper and lower sections of the case are surrounded by upper and lower bushings (10,11). The inner diameter of the bushings and the outer diameter of the case sections formed an outer bearing gap (12) which is filled with bearing fluid and which is connected to an inner bearing gap (5). A covering (7) is arranged facing the pressure plate (6) which is arranged at the outer circumference of the tubular case. The internal bearing gap is formed between the surfaces of the shaft, case, pressure plate and covering. Radial bearing areas (13,14) and axial bearing areas (19,20) are arranged with the case, pressure plate and covering.

Description

Field of the invention

The The invention relates to a fluid dynamic bearing system, in particular for pivotal mounting of a spindle motor e.g. for driving the storage disk (s) a hard disk drive.

spindle motors consist essentially of stator, rotor and at least one between these two parts arranged storage system. The electric motor driven rotor is with the help of the storage system against the Stator rotatably mounted. As a storage system, among other things rolling bearings, but recently used fluid dynamic storage systems preferred.

A known embodiment of a fluid dynamic bearing system, disclosed for example in the DE 201 19 716 U1 includes a fixed shaft and a bearing sleeve having an axial bore for receiving the shaft. The sleeve rotates freely around the fixed shaft and together with this forms a radial bearing. The mutually operatively connected shaft and sleeve bearing surfaces are spaced apart by a thin, concentric bearing gap filled with a lubricant. In at least one bearing surface, a surface structure is incorporated, which as a result of the rotational relative movement between sleeve and shaft exerts local acceleration forces on the lubricant in the bearing gap. In this way creates a kind of pumping action, which leads to the formation of a homogeneous and uniformly thick lubricant film within the bearing gap, which is stabilized by zones fluid dynamic pressure. The bearing sleeve carries a rotor bell on which eg disks of a hard disk drive are arranged.

A Displacement of the described arrangement along the axis of rotation is characterized by at least one appropriately designed fluid dynamic Thrust bearing prevents. In a fluid dynamic thrust bearing are the mutually interacting bearing surfaces of which at least one is provided with a surface structure, each arranged in a plane perpendicular to the axis of rotation and through a thin, preferably flat, filled with lubricant bearing gap axially from each other spaced. The provided for receiving the axial forces fluid dynamic Thrust bearing are preferably by the two end faces of a formed at the end of the shaft arranged pressure plate, wherein the one face the pressure plate has a corresponding end face of the sleeve and the other end face the inside end face associated with a cover. The cover thus forms an abutment to the pressure plate and closes the open side of the storage system and prevents air from entering the filled with lubricant Bearing gap penetrates.

Of the Trend goes to smaller and smaller spindle motors, especially smaller and smaller heights, which leads to a corresponding miniaturization of the storage systems, wherein it is difficult due to the ever smaller bearing distances is to achieve a required rigidity of the storage systems. The stiffness is one of the most important sizes for Determining the performance of a warehouse. In a fluid dynamic Warehouse hangs the runout (blow) to a great extent from the rigidity of the bearing.

The US 6,371,649 B1 , which is considered as the closest prior art, discloses in particular in 3 a fluid dynamic bearing system with a fixed shaft, a surrounding the shaft and rotatable about a rotation axis, tubular sleeve, at least one arranged on the outer circumference of the sleeve pressure plate, and a cover of the end faces of the pressure plate and the sleeve cover. Opposed surfaces of the shaft, sleeve, pressure plate, and cover spaced from each other by an inner bearing gap filled with a bearing fluid form at least one radial bearing portion and at least one thrust bearing portion. It is provided a bearing bush, wherein formed between the inner diameter of the bearing bush and the outer diameter of the sleeve outer bearing gap, which is connected to the inner bearing gap.

The US 2004/0240104 A1 discloses a spindle motor whose bearing system is divided into an upper and a lower bearing portion.

Disclosure of the invention

The The object of the invention is a fluid dynamic bearing system for spindle motors in such a way that even at low axial height a high bearing stiffness and rotational stability is achieved.

These The object is achieved by a Storage system solved with the features of claim 1.

Further preferred and advantageous embodiments of the invention are in the dependent claims specified.

The fluid dynamic La invention The system comprises a fixed shaft, a tubular sleeve surrounding the shaft and rotatable about an axis of rotation, and at least one pressure plate disposed on the outer circumference of the sleeve, and a cover closing the end faces of the pressure plate and the sleeve, facing one another and filled with a bearing fluid inner bearing gap spaced surfaces of the shaft, the sleeve, the pressure plate and the cover at least form a radial bearing region and at least one thrust bearing region. The sleeve has on its outer periphery a collar, which divides the sleeve into an upper and a lower portion, wherein the upper portion of an upper bearing bush and the lower portion is surrounded by a lower bearing bush, so that between the inner diameter of the bearing bushes and the outer diameter of the two portions of the sleeve forms a bearing fluid filled with outer bearing gap, which is connected to the inner bearing gap.

First and second radial bearing areas are defined by the inner bearing gap spaced-apart surfaces the upper portion of the sleeve and the shaft and the lower portion of the sleeve and the shaft formed.

third and fourth radial bearing areas are separated by the outer bearing gap spaced surfaces the upper portion of the sleeve and the upper bushing and the lower portion of the sleeve and the lower bearing bush formed.

It Preferably, two thrust bearing areas are provided by spaced-apart surfaces the pressure plate and the cover and the pressure plate and the faces the upper bearing bush are formed. The radial storage areas and the thrust bearing areas are characterized by surface structures, applied to at least one of the paired bearing surfaces are.

The high rigidity of the fluid dynamic bearing according to the invention is through a higher Number of radial or thrust bearing areas achieved, as well as a preferably huge Bearing clearance of radial bearings.

by virtue of the nested arrangement of the upper thrust bearing and the upper radial bearing is saved axial space, whereby the Construction comparatively flat bearing is possible.

The central part of this arrangement according to the invention is the tubular sleeve, the forms part of the rotating part of the bearing. This sleeve forms together with the upper and lower bushings an upper and a lower radial bearing. The outer diameter and the inner diameter of the sleeve may preferably be used to form further radial bearing areas be used.

at Use of an upper thrust bearing can be on the outer upper Radial bearing formed between the outer diameter of the sleeve and the upper bushing, be waived.

By on both sides of the sleeve arranged radial bearing areas increases according to the invention, the rigidity of the camp. The arranged, for example, in the upper region of the sleeve Pressure plate forms together with the cover plate and the upper bearing bush two thrust bearing areas. Preferably at the other end of the sleeve, or at any point of the sleeve, can additional pressure plates are arranged to increase the axial stiffness increase.

The Upper side of the bearing is an example of use or arrangement a radial bearing and a thrust bearing in the same plane vertically to the axis of rotation. The pressure plate is on the outer side of the sleeve during the Radial bearing is arranged on the inside. This results a maximum possible Bearing distance between the upper and / or lower radial bearing (s), which reduces the radial impact of the bearing.

Around a best possible To ensure circulation of the bearing fluid in the bearing gaps, are the outer and the the inner bearing gap preferably arranged in the sleeve radial bores or connecting channels directly connected.

Further For example, the shaft may preferably have a constriction which together with the sleeve forms a cavity into which the open ends of the inner Storage gap open. The cavity is in the transition areas to the inner bearing gap partially filled with bearing fluid and serves to seal the inner bearing gaps and as a reservoir for the Bearing fluid.

In addition, can the shaft holes or channels for ventilation of the constriction formed cavity, so that a pressure equalization in the cavity and other areas of the storage system.

The sleeve preferably has on its half length a collar which connects the sleeve with the other parts of the rotor, in particular the rotor bell. The sleeve and the collar can be formed in one or more parts. The forehead Chen this federal can also be used as thrust bearing together with the end faces of the corresponding bushings.

The entire bearing is attached to both ends of the fixed shaft. At one end, the shaft is firmly received in a base plate. At the other end, the shaft with a screw on a housing part be attached. The two-sided attachment of the shaft also contributes to increase the Stiffness of the bearing and thus reduces the impact.

Summary the drawing

following is an embodiment of Invention described in more detail with reference to the drawing figure

1 shows a schematic sectional view of a spindle motor with the inventive design of the storage system.

description a preferred embodiment the invention

1 shows a schematic sectional view of a spindle motor for driving a hard disk drive with a fluid dynamic bearing system according to the invention.

The spindle motor includes a fixed base plate 1 , In an opening of the base plate 1 is a wave 2 arranged and fixed to the base plate 1 connected. The wave 2 is from one to an axis of rotation 3 rotatable tubular sleeve 4 surrounded, wherein the inner diameter of the sleeve 4 is slightly larger than the outer diameter of the shaft 2 , so between sleeve 4 and wave 2 an inner bearing gap 5 remains, which is filled with a bearing fluid, preferably a bearing oil. At the outer circumference of the sleeve 4 is - preferably at one or both ends - a disc-shaped pressure plate 6 arranged partially by another upper bushing described in more detail below 10 is surrounded. The front sides of the printing plate 6 and the sleeve 4 are through a cover 7 locked. The wave 2 is through a central hole of the cover 7 passed through.

Between the facing surfaces of the printing plate 6 , the cover 7 and the upper bearing bush 10 is also a bearing gap 8th defined with the inner bearing gap 5 connected is.

The sleeve 4 has on its outer circumference - about halfway - a covenant 9 who the sleeve 4 in an upper section 4a and a lower section 4b divided. The upper section 4a the sleeve 4 is from an upper bushing 10 and the lower section 4b from a lower bushing 11 surround. The inner diameter of the sleeve 4 receiving axial bores of the two bushings 10 . 11 is slightly larger than the outer diameter of the sleeve 4 , so that between the surfaces of the bearing bushes 10 . 11 and the associated portions of the sleeve 4 an outer bearing gap filled with bearing fluid 12 training that over the bearing gap 8th with the inner bearing gap 5 connected is. The upper bearing bush 10 is stuck with the cover 7 connected, in turn, fixed to the upper section of the shaft 2 connected is. The lower bearing bush 11 is non-rotatable on the shaft 2 arranged.

The upper bearing bush 10 has a first annular recess in which the pressure plate 6 is included. The cover 7 is in a second larger diameter recess in the upper bushing 10 picked up and seals the bearing assembly tight.

The illustrated bearing arrangement comprises at least two, but preferably three radial bearing areas 13 . 14 . 16 , whereby a very high rigidity of the storage system is achieved. However, the invention is not limited to these embodiments. For example, the use of further, such as a fourth radial bearing area on the outside of the upper sleeve portion 4a possible below the thrust bearing.

The through the inner bearing gap 5 spaced-apart surfaces of the upper portion 4a the sleeve 4 and the wave 2 define a first radial bearing area 13 , Accordingly, those defined by the inner bearing gap 5 spaced-apart surfaces of the lower portion 4b the sleeve 4 and the wave 2 a second radial bearing area 14 ,

In a known manner, the radial bearing areas are surface structures 17 . 18 , For example, a groove pattern, which on at least one of the paired bearing surfaces, such as the surface of the shaft 2 , are applied. Of course, these surface structures may also be on the corresponding opposite surface of the sleeve 4 be arranged. Once the movable sleeve 4 is rotated due to the surface structures 17 . 18 in the inner bearing gap 5 a fluid dynamic pressure on, so that the radial bearings 13 . 14 become sustainable.

The axial forces of the bearing system are by two oppositely acting thrust bearings 19 . 20 added. The first thrust bearing 19 is due to the spaced surfaces of the printing plate 6 and the cover 7 defined while the second thrust bearing 20 through the spaced apart surfaces of the printing plate 6 and the front of the upper bearing sleeve 10 is formed. The thrust bearing areas 19 . 20 are characterized by helical surface structures that are applied to at least one of the paired bearing surfaces and exert a pumping action on the bearing fluid. The shape and configuration of the surface structures is known to a person skilled in the art and therefore not further illustrated in the drawing.

To improve the rigidity of the bearing system is preferably another radial bearing area 16 intended. A third radial bearing area may be through the outer surfaces of the upper section 4a the sleeve 4 and the upper bearing bush 10 be defined by the outer bearing gap 12 spaced apart from each other (not shown). The also through the outer bearing gap 12 spaced-apart surfaces of the lower portion 4b the sleeve 4 and the lower bearing bush 11 form a fourth radial bearing 16 , Also these radial storage areas 15 . 16 are characterized by surface structures (not shown).

It can be seen that the outer bearing gap 12 over the pressure plate 6 surrounded section of the bearing gap 8th with the inner bearing gap 5 connected is. Furthermore, the sleeve 4 preferably a plurality of bores or connecting channels 21 . 22 having the outer and the inner bearing gap 12 . 5 additionally connect with each other, allowing a direct exchange of bearing fluid between the two bearing gaps 12 . 5 is ensured.

The sleeve 4 forms together with the pressure plate the moving part of the storage system. At the federal government 9 the sleeve 4 is the rotor bell 23 attached to the spindle motor. The outer diameter of the federal government 9 is preferably greater than the outer diameter of the two bushings 10 . 11 so that the rotor bell 23 and covenant 9 can be connected to each other by means of a press connection.

When the spindle motor is inserted in a disk drive, the rotor bell is supported 23 one or more storage disks (not shown) and drives them in rotation.

The necessary for the operation of the spindle motor electro-magnetic components are on the base plate 1 or the rotor bell 23 arranged. The base plate 1 carries a stator assembly 24 consisting of a plurality of stator windings. The stator windings are annularly spaced from permanent magnets 25 Surrounded by the rotor bell 23 are attached.

The wave 2 preferably has half the length, preferably at the level of the federal government 9 , a constriction on, so that in this area between the sleeve 4 and the wave 2 a cavity 26 forms. The sections of the inner bearing gap 5 open into the cavity 26 , In the transition areas to the inner bearing gap 5 the cavity tapers 26 in the direction of the bearing column 5 and forms sealing regions, so-called "visco-seals." These sealing regions are partially filled with bearing fluid and serve on the one hand as a reservoir for the bearing fluid and on the other hand for sealing the bearing gaps 5 ,

The open ends of the outer bearing gap 12 lead into interstices 27 between the faces of the covenant 9 and the end faces of the respective opposite bushings 10 respectively. 11 , In order here too leakage of the bearing fluid from the bearing gap 12 or to prevent the ingress of dirt into the bearing gap, conical sealing regions or also just sealing regions with a very small opening angle can be provided as seals.

In the wave 2 are holes or channels 28 provided, which defines the cavity defined by the constriction 26 Connect to the ambient atmosphere and ensure pressure equalization in the storage system.

1

baseplate

2

wave

3

axis of rotation

4

shell

4a

sleeve section (above)

4b

sleeve section (below)

5

bearing gap (Inside)

6

printing plate

7

cover

8th

bearing gap (Thrust bearing)

9

Federation

10

bearing bush (upper)

11

bearing bush (lower)

12

bearing gap (Outside)

13

Radial bearing region

14

Radial bearing region

15

Radial bearing region

16

Radial bearing region

17

surface structure

18

surface structure

19

thrust

20

thrust

21

connecting channel

22

connecting channel

23

rotor bell

24

stator

25

permanent magnets

26

cavity (Constriction)

27

gap

28

channels

Claims (18)

Fluid dynamic bearing system for pivotally mounting a spindle motor for driving the hard drive (s) of a hard disk drive, comprising a stationary shaft ( 2 ) surrounding a shaft and about an axis of rotation ( 3 ) rotatable, tubular sleeve ( 4 ), at least one pressure plate arranged on the outer circumference of the sleeve ( 6 ), and one of the end faces of the pressure plate and the sleeve occlusive cover ( 7 ), wherein facing each other and by a filled with a bearing fluid inner bearing gap ( 5 . 8th ) spaced apart surfaces of the shaft ( 2 ), the sleeve ( 4 ), the pressure plate ( 6 ) and the cover ( 7 ) at least one radial bearing area ( 13 ; 14 ) and at least one thrust bearing region ( 19 ; 20 ), the sleeve ( 4 ) on its outer circumference a collar ( 9 ), the sleeve ( 4 ) into an upper and a lower section ( 4a . 4b ), wherein the upper portion of an upper bearing bush ( 10 ) and the lower portion of a lower bushing ( 11 ) is surrounded, so that between the inner diameter of the bearing bushes ( 10 . 11 ) and the outer diameter of the two sections of the sleeve ( 4 ) filled with bearing fluid outer bearing gap ( 12 ) formed with the inner bearing gap ( 5 ) connected is. Fluid dynamic bearing system according to claim 1, characterized in that through the inner bearing gap ( 5 ) spaced apart surfaces of the upper portion ( 4a ) of the sleeve and the shaft ( 2 ) a first radial bearing area ( 13 ) train. Fluid dynamic bearing system according to one of the preceding claims, characterized in that through the inner bearing gap ( 5 ) spaced apart surfaces of the lower portion ( 4b ) of the sleeve and the shaft ( 2 ) a second radial bearing area ( 14 ) train. Fluid dynamic bearing system according to one of the preceding claims, characterized in that through the outer bearing gap ( 12 ) spaced apart surfaces of the upper portion ( 4a ) of the sleeve and the upper bearing bush ( 10 ) form a third radial bearing area. Fluid dynamic bearing system according to one of the preceding claims, characterized in that through the outer bearing gap ( 12 ) spaced apart surfaces of the lower portion ( 4b ) of the sleeve and the lower bearing bush ( 11 ) a fourth radial bearing area ( 16 ) train. Fluid dynamic bearing system according to one of the preceding claims, characterized in that spaced-apart surfaces of the pressure plate ( 6 ) and the cover ( 7 ) a first thrust bearing region ( 19 ) train. Fluid dynamic bearing system according to one of the preceding claims, characterized in that spaced-apart surfaces of the pressure plate ( 6 ) and the upper bearing sleeve ( 10 ) a second thrust bearing region ( 20 ) train. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the radial bearing areas ( 13 . 14 . 16 ) and the thrust bearing areas ( 19 . 20 ) by surface structures ( 17 . 18 ), which are applied to at least one of the paired bearing surfaces. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the sleeve ( 4 ) at least one connection channel ( 21 . 22 ) having the inner bearing gap ( 5 ) with the outer bearing gap ( 12 ) connects. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the lower bearing bush ( 11 ) rotatably on the shaft ( 2 ) is arranged. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the cover ( 7 ) rotatably on the shaft ( 2 ) is arranged. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the shaft ( 2 ) has a constriction, which together with the sleeve ( 4 ) a cavity ( 26 ), in which the open ends of the inner bearing gap ( 5 ). Fluid dynamic bearing system according to one of the preceding claims, characterized in that the cavity ( 26 ) in the transition areas to the inner bearing gap ( 5 ) is partially filled with bearing fluid. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the shaft ( 2 ) Holes or channels ( 28 ) for venting through the constriction formed cavity ( 26 ) having. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the outer diameter of the Federal ( 9 ) is greater than the outer diameter of the two bushings ( 10 . 11 ). Fluid dynamic bearing system according to one of the preceding claims, characterized in that the collar ( 9 ) with a rotor bell ( 23 ) of the spindle motor is connected. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the shaft ( 2 ) rotatably in a base plate ( 1 ) of the spindle motor is received. Fluid dynamic bearing system according to one of the preceding claims, characterized in that the upper side of the shaft ( 2 ) is rotatably connected to a cover.