DE102007036790A1 - Fluid dynamic bearing system for pivot bearing of motors, particularly spindle motor for fixed disk drive or blower, has fixed bearing components where shell of components forms angle between zero to ten degree with rotation axis - Google Patents

Abstract

The fluid dynamic bearing system has fixed bearing component (10) where shell (52) of the components forms an angle between 0 degree to 10 degree with the rotation axis (16). The shell (56) of the movable bearing component (12) forms another angle between 0 degree to 10 degree with the rotation axis in area of the sealing gap (48). The two angles open in the same direction.

Description

Field of the invention

The The invention relates to a fluid dynamic bearing system, which at least a radial bearing and at least one thrust bearing comprises, according to the features of the preamble of claim 1. Such fluid dynamic bearings be about to pivot bearings of motors, such as spindle motors used in turn to drive disk drives, fans or similar serve.

State of the art

fluid Dynamic Bearings, as used in spindle motors, include in usually at least two relatively rotatable bearing components, the bearing surfaces assigned to one another with a bearing fluid, z. As air or bearing oil, filled Training camp gap. In a known manner associated with the storage areas and surface structures acting on the bearing fluid. In fluid dynamic bearings, the surface structures in the form of Wells or surveys usually applied to one or both of the opposing bearing surfaces. These on appropriate storage areas the bearing partners arranged surface structures serve as storage and / or pumping structures that upon relative rotation of the bearing components create a hydrodynamic pressure within the bearing gap. For radial bearings, for example, sinusoidal, parabolic or herringbone grooved surface structures used perpendicular to the axis of rotation of the bearing components on the Scope of at least one bearing component are distributed. Axial bearings, for example, spiral groove-shaped surface structures used, which are usually arranged vertically about a rotation axis become. In a fluid dynamic bearing of a spindle motor for driving Hard disk drives according to a known type is a shaft in a bearing bore of a bearing bush rotatably mounted. The diameter of the hole is slightly larger than the diameter of the shaft so that between the surfaces of the Bearing bush and the shaft one filled with a bearing fluid bearing gap remains. The facing surfaces of the shaft and / or the bearing bush have pressure generating bearing structures as part of at least a fluid dynamic radial bearing. A free end of the wave is connected to a hub whose bottom surface together with an end face of the Bushing forms a fluid dynamic thrust bearing. This is one of the facing surfaces of the hub or the bearing bush provided with pressure generating bearing structures.

fluid Dynamic Storage systems for the use in spindle motors must be built so that as possible no bearing fluid from the bearing gap in other areas of the spindle motor can escape. On the one hand reduces emerging from the bearing gap Bearing fluid the life of the storage system, as for example the Risk of dry running of the bearing exists, and on the other hand, soiling Bearing fluid other components of the spindle motor. The leakage of Bearing fluid from the bearing gap is therefore due to appropriate sealing arrangements prevented. Often, so-called capillary seals are used Insert, which connect to the open end of the bearing gap and a Prevent leakage of bearing fluid into the engine. The bearing fluid is retained in the capillary seal by capillary forces, which is in the sealing gap also a vapor barrier by vaporizing bearing fluid at the transition between the bearing fluid and the air present in the capillary seal forms.

Disclosure of the invention

It The object of the invention is a fluid dynamic bearing system specify the type mentioned, compared to known Storage systems a higher Life, improved shock resistance and improved Retention capacity for the bearing fluid has in the bearing gap, especially at high speeds of 10,000 Revolutions per minute or more.

These The object is achieved by a Storage system with pressure generating groove-shaped surface structures according to the characteristics of Patent claim 1 solved.

preferred Embodiments and further advantageous features of the invention are in the dependent claims specified.

The fluid-dynamic bearing system comprises at least one stationary and at least one movable bearing component, which are rotatable relative to one another about a common axis of rotation and form a bearing gap filled with a bearing fluid between mutually associated bearing surfaces. On one side of the bearing gap, a sealing gap follows, which is arranged between a radially outwardly directed lateral surface of the fixed bearing component and a radially inwardly directed circumferential surface of the movable bearing component, and at least partially filled with bearing fluid. According to the invention, in the region of the sealing gap, the lateral surface of the movable bearing component with the axis of rotation has a first angle between 0 ° and 10 ° and the lateral surface of the stationary bearing component with the axis of rotation a second Angle between 0 ° and 10 ° forms, with the two angles open in the same direction.

Around leakage and also evaporation of bearing fluid in the area of the capillary seal To minimize, the sealing gap is very narrow but still im Comparison to the dimensions of the bearing gap by one or two orders of magnitude greater. It is also sought to make the sealing gap very long, on the one hand to bring a corresponding supply of bearing fluid there to be able to and to the other, to the length to increase the diffusion barrier.

According to the invention is thus a sealing gap is provided which extends over part of the outer periphery of the fixed bearing member and preferably its width is very small. Due to the small width and the relative length of the Sealing gap results in a low evaporation rate of the Sealing gap located bearing fluid, resulting in a long life the fluid dynamic storage system ensures.

In a preferred embodiment of the invention comprises the fixed Bearing component a bearing bush with a central bearing bore, and the movable bearing member rotatable in the bearing bore mounted shaft. The free end of the shaft is with a cup-shaped component connected as part of the hub which forms the bearing bush under formation partially surrounds the sealing gap.

In known manner are on the wall of the central bearing bore and / or on the surface the shaft pressure generating bearing structures formed as part of at least one fluid dynamic radial bearing. On the face of the Bearing bush and / or one of these face opposite surface of the cup-shaped member are also pressure-generating bearing structures formed as part a fluid dynamic thrust bearing.

Of the Seal gap begins radially outside the thrust bearing and then sets in the axial direction along the outer surface of the Bushing continues. The axial length the sealing gap is at least a quarter of the length the bearing bush.

In a first embodiment of the invention are the by the lateral surfaces the fixed or the movable bearing component and the axis of rotation included angles each 0 °, the is called the assigned lateral surfaces are cylindrical and parallel to the axis of rotation. such cylindrical lateral surfaces, which form the boundaries of the sealing gap can be very be processed precisely and above all with a low surface roughness. A low surface roughness has a positive effect on the capillary forces, which are due to the Seal gap existing bearing fluid act and cause the sealing effect. reinforced this capillary action is due to the above-mentioned relative length of the Sealing gap and its small width. All of these factors add up become a reliable one Sealing effect of the sealing gap. Due to the low surface roughness also results in a relatively low acceleration effect the bearing fluid in the sealing gap. The two opposite lateral surfaces rotate relative to each other and cause an acceleration of the Bearing fluid in the direction of rotation. Very smooth surfaces reduce this Acceleration effect and lead for better stability the forming surface tension at the interface between bearing fluid and air.

In In another preferred embodiment of the invention, the angle is the lateral surface of the movable component of the bearing forms with the rotation axis, 0 °, during the Angle that the fixed component forms with the axis of rotation, 0 ° to 10 °. Thereby the sealing gap widens in the direction of its open end on. Furthermore, in addition to those associated with the first Embodiment of the invention described advantages and effects another effect of increasing the sealing effect, which is based on the centrifugal force, which is exerted upon rotation of the bearing components on the bearing fluid. The centrifugal force accelerates the bearing fluid radially outward. By the beveled lateral surface the bearing bush, the bearing fluid is opposite to the opening of the Sealing gap pressed into the sealing gap due the acting centrifugal forces. This results in an additional Safety against leakage of bearing fluid from the sealing gap.

In a third embodiment of the invention may be provided that both angles are opposite lateral surfaces greater than 0 ° are, the opening both angle is opposite to the vertex of the angle. With In other words, the respective diameter of the lateral surfaces of the both bearing components in the area of the apex of the angle greater than the diameter of the bearing components in the area of the opening of the Seal gap. Preferably, the first angle is greater than the second angle so that the sealing gap widens in the direction of its opening.

In yet another embodiment of the invention, the diameter of the lateral surface of the movable bearing component changes in two or more stages and decreases in particular with increasing proximity to the opening of the sealing gap. In this case, a tangent applied to the lateral surface forms a leg of the second angle out. In the same way, the diameter of the lateral surface of the fixed bearing component may change in two or more stages, wherein a tangent applied to this lateral surface forms a leg of the first angle. Preferably, a plurality of gradations are provided on the lateral surfaces, wherein the gradations of the two lateral surfaces are preferably arranged offset from one another with respect to an imaginary line parallel to the axis of rotation. This stepwise design of the sealing gap defining lateral surfaces has the advantage that the level of the bearing fluid in the sealing gap can be visually recognized and tested well. Each step in the lateral surfaces acts as a kind of visual marker, from which the level of the bearing fluid in the sealing gap can be read off.

in the The area of the open end of the sealing gap can be either on fixed or provided on the movable bearing component a ringfömige groove be that as a barrier to possibly still escaping bearing fluid is used.

The The invention relates in particular to a fluid dynamic bearing system for one Spindle motor as used to drive hard disk drives can be.

The The invention will now be described with reference to preferred embodiments explained in more detail on the drawings described below. This results in Further features, advantages and possible applications of the invention.

Brief description of the drawings

1 shows a longitudinal section through a spindle motor with a first embodiment of a fluid dynamic bearing according to the invention.

2 shows a longitudinal section through a spindle motor in a opposite 1 slightly modified design.

3 shows a longitudinal section through a spindle motor with a second embodiment of a fluid dynamic bearing according to the invention.

4 shows a longitudinal section through a spindle motor with a third embodiment of a fluid dynamic bearing according to the invention.

5 shows an enlarged longitudinal section of the region of the sealing gap of 4 ,

6 shows a longitudinal section through a spindle motor with a fourth embodiment of a fluid dynamic bearing according to the invention.

7 shows an enlarged longitudinal section of the region of the sealing gap of 6 ,

Description of preferred embodiments the invention

The 1 shows a section through a spindle motor with a fluid dynamic bearing system according to the invention. The spindle motor includes a fixed bushing 10 having a central bore and forming the fixed component of the storage system. Into the bore of the bearing bush 10 is a wave 12 used, whose diameter is slightly smaller than the diameter of the bore. Between the surfaces of the bearing bush 10 and the wave 12 there remains a bearing gap 14 , The opposite surfaces of the shaft 12 and the location socket 10 form two fluid dynamic radial bearings 18 . 22 out, by means of which the shaft 12 around a rotation axis 16 rotatable in the bearing bush 10 is stored. The radial bearings 18 . 22 are through storage structures 20 . 24 marked on the surface of the shaft 12 and / or the bearing bush 10 are applied. The bearing gap 14 is filled with a suitable bearing fluid, such as a bearing oil. The storage structures 20 . 24 practice with rotation of the shaft 12 a pumping action on the in the bearing gap 14 between wave 12 and bearing bush 10 located bearing fluid, so that the radial bearings 18 . 22 become sustainable.

At the bottom of the shaft 12 is a one-piece with the shaft or a separately formed stopper ring 13 arranged, which has an enlarged outer diameter compared to the shaft diameter. The stopper ring prevents the shaft from falling out 12 from the bushing 10 , The bearing is on this side of the bearing bush 10 through a cover plate 34 locked.

A free end of the wave 12 is with a pot-shaped component 26 connected, which partially surrounds the bearing bush. A lower, flat surface of the cup-shaped component 26 forms together with an end face of the bearing bush 10 a fluid dynamic thrust bearing 28 out. Here, the end face of the bearing bush 10 or the opposite surface of the cup-shaped component 26 with storage structures 30 provided during rotation of the shaft 12 a pumping action on the in the bearing gap 14 between the component 26 and end face of the bearing bush 10 located bearing fluid exerts, so that the thrust bearing 28 becomes sustainable. In the bearing bush, a recirculation channel 32 be provided, the one at the outer edge of the thrust bearing 28 located section of the storage gap 14 with one below the lower radial bearing 22 located section of the storage gap 14 interconnects and supports a circulation of the bearing fluid in the camp.

The bearing bush 10 is in a base plate 36 arranged the spindle motor. On the cup-shaped component 26 is an annular hub 38 arranged, which has on its outer circumference a peripheral edge. The components 26 and 38 Of course, also be formed in one piece. The bearing bush 10 surrounding is a stator assembly 40 on the base plate 36 arranged, which consists of a ferromagnetic laminated stator core and corresponding stator windings. This stator arrangement 40 is surrounded by an annular rotor magnet 42 which is in a return ring 44 is arranged with a larger diameter and the inner circumference of the circumferential edge of the hub 38 is attached. Shown is an external rotor motor. Alternatively, of course, an internal rotor motor can be used. Below the rotor magnet 42 is a ferromagnetic metal ring 46 arranged, which attracts the rotor magnet, causing a downward to the base plate 36 directed force results. This force is used for the axial preload of the bearing system.

The bearing gap 14 includes an axial section extending along the shaft 10 and the radial bearing 18 . 22 extends, and a radial portion extending along the end face of the bearing bush 10 and the thrust bearing 28 extends. At the radially outer end of its radial portion of the bearing gap is 14 in a gap with a larger gap distance over, which partially as a sealing gap 48 acts. The gap initially extends from the bearing gap 14 radially outwardly and merges into an axial section extending along the outer circumference of the bushing 10 between the bearing bush 10 and a cylindrical portion of the cup-shaped member 26 extends and the sealing gap 48 forms. With a diameter of the bearing bush 10 of a few millimeters, the width of the sealing gap 48 typically 50-300 microns.

The outer surface of the bearing bush 10 and the inner circumferential surface of the cup-shaped component 26 are cylindrical and form the boundary of the sealing gap 48 , Thus, the sealing gap runs 48 parallel to the axis of rotation 16 , Such cylindrical lateral surfaces, which are the boundaries of the sealing gap 48 form, can be processed very precisely and, above all, with a low surface roughness and set the bearing fluid to a low frictional resistance. At the end of the sealing gap 48 can the bushing 10 a groove on the outer circumference 50 provided with, for example, an oil-stop varnish to prevent migration of the bearing fluid beyond this barrier.

2 essentially shows the same spindle motor as 1 , wherein the same components are provided with the same reference numerals. In contrast to 1 is at 2 the groove 150 not on the outer circumference of the bearing bush 110 , but on the inner circumference of the cup-shaped component 26 intended. Another difference is the design of the cover plate 134 that in contrast to 1 is flat. The stopper ring 13 on the shaft is in this case in a separate recess of the bearing bush 110 arranged.

3 shows a section through a further embodiment of a spindle motor according to the invention, with respect to 1 the same components are provided with the same reference numerals.

A major difference of the spindle motor from 3 across from 1 is that the outer shell surface 252 the bearing bush 210 in the area of the sealing gap 248 is bevelled. The angle between the lateral surface 252 the bearing bush 210 and the rotation axis 16 is in this case greater than 0 ° and is for example 3 °. The apex of the angle is in the region of the beginning of the sealing gap 248 , wherein the angle to the opening of the sealing gap 248 opens. The lateral surface 256 the opposite edge of the cup-shaped component 26 is inclined by an angle which is smaller (or equal) to the angle of inclination enclosed by the lateral surface 252 the bearing bush 210 and the rotation axis 16 so that the sealing area 248 extended conically towards the bottom. The angle that the lateral surface 252 the bearing bush 210 with the rotation axis 16 can also vary over the length of the lateral surface, as seen from 3 evident. Here, the angle runs from the beginning of the sealing gap 248 initially constant at a smaller angle, for example 3 ° and increases in the last third of the sealing gap 48 for example, at 5 ° and ends in a corresponding groove 250 the bearing bush 210 , Due to the centrifugal force, the bearing fluid is accelerated radially outward and through the beveled lateral surface 252 the bearing bush 210 pressed into the sealing gap and held therein. This results in an additional sealing effect.

4 shows opposite 3 a modified embodiment of a spindle motor. An enlarged view of the area of the sealing gap 448 is in 5 shown. Compared to 3 are in the 4 and 5 the same components provided with the same reference numerals. In this example, the lateral surface is 356 of the cup-shaped component 26 in the area of the sealing gap 348 cylindrically formed, while the lateral surface 352 the bearing bush 310 in the area of the sealing gap 348 is tapered inwards and, for example, based on the axis of rotation 16 has an angle between 3 ° and 5 °. It is important that the man telflächen of the bearing bush 310 and the cup-shaped component 26 at the beginning of the sealing gap 348 are cylindrical, and the lateral surface of the bearing bush 310 only after a third to half of the sealing gap 348 inward at the intended angle. At the end of the inclined lateral surface 352 is the groove again 350 provided, which limits the sealing gap.

6 Finally shows a further embodiment of the spindle motor according to the invention in which, based on the preceding drawing figures, the same components are provided with the same reference numerals.

7 shows an enlarged view of the area of the sealing gap 448 from 6 ,

In contrast to the previous embodiments of the storage system, in particular the sealing gap, the sealing gap 448 according to the 5 and 6 no uniform surface, but is graded. So z. B. the lateral surface 452 the bearing bush 410 in the area of the sealing gap 448 with gradations 454 provided, whereby the diameter of the bearing bush 410 in the direction of the opening of the sealing gap 448 reduced. Between the individual stages 454 has the lateral surface 452 the bearing bush 410 cylindrical sections on. In the same way, the lateral surface runs 456 of the cup-shaped component 426 in the area of the sealing gap 448 not even but has a variety of levels 458 on, so that the inner diameter of the cup-shaped component 426 for opening the sealing gap 448 downsized. Again, you can choose between each step 458 cylindrical sections of the lateral surface 456 be provided. Preferably, the stages are located 454 and 458 not at the same height, but are offset from each other. It is Z. But also possible, the lateral surface of the bearing bush 410 Shaped form in the illustrated manner, while the lateral surface of the cup-shaped component 426 is straight and cylindrical, such. In 1 shown.

The steps allow the level of the bearing fluid in the sealing gap 448 Reliable visually or mechanically check. Each step in the lateral surfaces acts as a kind of visual marker, from which the level of the bearing fluid can be read off.

10

bearing bush

12

wave

13

stopper ring

14

bearing gap

16

axis of rotation

18

radial bearings

20

surface structures

22

radial bearings

24

surface structures

26

Pot-shaped component

28

axial bearing

30

warehouse structures

32

recirculation

34

cover

36

baseplate

38

hub

40

stator

42

rotor magnet

44

Return ring

46

metal ring

48

seal gap

50

groove

52

Lateral surface (bearing bush)

56

Lateral surface (component)

110

bearing bush

134

cover

150

groove

210

bearing bush

248

seal gap

250

groove

252

Lateral surface (bearing bush)

256

Lateral surface (component)

310

bearing bush

348

seal gap

350

groove

352

Lateral surface (bearing bush)

356

Lateral surface (component)

410

bearing bush

426

448

seal gap

450

groove

452

Lateral surface, (bearing bush)

454

step

456

Lateral surface (component)

458

step

Claims (18)

Fluid dynamic storage system with at least one fixed ( 10 ; 210 ; 310 ; 410 ) and at least one movable bearing component ( 12 . 26 ) relative to each other about a common axis of rotation ( 16 ) are rotatable and between bearing surfaces associated with a bearing fluid filled with a bearing gap ( 14 ), wherein on one side of the bearing gap a sealing gap ( 48 ; 248 ; 348 ; 448 ), which between a radially outwardly directed lateral surface ( 52 ; 252 ; 352 ; 452 ) of the fixed bearing component ( 10 ; 210 ; 310 ; 410 ) and one of these opposite, radially inwardly directed lateral surface ( 56 ; 256 ; 356 ; 456 ) of the movable bearing component and is at least partially filled with bearing fluid, characterized in that in the region of the sealing gap ( 48 ; 248 ; 348 ; 448 ) the lateral surface ( 52 ; 252 ; 352 ; 452 ) of the fixed bearing component ( 10 ; 210 ; 310 ; 410 ) with the rotation axis ( 16 ) a first angle between 0 ° -10 ° and the lateral surface ( 56 ; 256 ; 356 ; 456 ) of the movable bearing component ( 12 . 26 ) with the rotation axis ( 16 ) forms a second angle between 0 ° -10 °, the two angles opening in the same direction. Fluid dynamic bearing system according to claim 1, characterized in that the sealing gap ( 48 ; 248 ; 348 ; 448 ) forms a capillary seal together with the bearing fluid therein. Fluid dynamic bearing system according to claim 1 or 2, characterized in that the length of the sealing gap ( 48 ; 248 ; 348 ; 448 ) at least a quarter of the axial length of the fixed bearing component ( 10 ; 210 ; 310 ; 410 ) is. Fluid dynamic bearing system according to one of claims 1 to 3, characterized in that the fixed component is a bearing bush ( 10 ; 210 ; 310 ; 410 ) comprising a central bearing bore. Fluid dynamic bearing system according to one of claims 1 to 4, characterized in that the movable bearing component rotatably mounted in the bearing bore shaft ( 12 ) whose free end is connected to a cup-shaped component ( 28 ), which is the bearing bush ( 10 ; 210 ; 310 ; 410 ) forming the sealing gap ( 48 ; 248 ; 348 ; 448 ) partially surrounds. Fluid dynamic bearing system according to claim 4 or 5, characterized in that on the wall of the central bearing bore and / or on the surface of the shaft ( 12 ) Pressure producing bearing structures ( 20 ; 24 ) are formed as part of at least one fluid dynamic radial bearing ( 18 ; 22 ). Fluid dynamic bearing system according to one of claims 4 to 6, characterized in that on an end face of the bearing bush ( 10 ; 210 ; 310 ; 410 ) and / or one of said end face opposite surface of the cup-shaped member ( 28 ) Pressure producing bearing structures ( 30 ) are formed as part of a fluid dynamic thrust bearing ( 28 ). Fluid dynamic storage system according to one of claims 1 to 7, characterized in that the first and the second angle 0 ° and the associated lateral surfaces are cylindrical. Fluid dynamic storage system according to one of claims 1 to 7, characterized in that the first angle between 0 ° -10 ° and the second angle is 0 °. Fluid dynamic storage system according to one of claims 1 to 7, characterized in that the first angle and the second Angle greater than 0 ° are. Fluid dynamic bearing system according to one of claims 1 to 10, characterized in that the first angle over the axial length of the lateral surface ( 252 ; 352 ; 452 ) of the stationary component ( 10 ; 210 ; 310 ; 410 ) changes. Fluid dynamic bearing system according to one of claims 1 to 11, characterized in that the second angle over the axial length of the lateral surface ( 256 ; 356 ; 456 ) of the movable bearing component ( 12 ; 26 ) changes. Fluid dynamic bearing system according to one of claims 1 to 12, characterized in that the diameter of the lateral surface ( 456 ) of the movable bearing component ( 12 . 26 ) in two or more stages ( 458 ), one on this lateral surface ( 456 ) tangent forms a leg of the first angle. Fluid dynamic bearing system according to one of claims 1 to 13, characterized in that the diameter of the lateral surface ( 452 ) of the fixed bearing component ( 410 ) in two or more stages ( 454 ), one on this lateral surface ( 452 ) applied tangent forms a leg of the second angle. Fluid dynamic bearing system according to one of claims 1 to 14, characterized in that the sealing gap ( 48 ; 248 ; 348 ; 448 ) is open to the ambient atmosphere, and at the open end of the sealing gap an annular groove or groove ( 150 ; 250 ; 350 ; 450 ) is provided on the fixed or on the movable bearing component. Spindle motor with a fluid dynamic bearing system according to claims 1 to 15, a base plate ( 36 ) for receiving the stationary bearing component ( 10 ; 110 ; 210 ; 310 ; 410 ) of the storage system, one with the movable bearing component ( 12 ; 26 ) connected hub ( 38 ) and an electromagnetic drive system ( 40 ; 42 ; 44 ) for driving the movable bearing component ( 12 ; 26 ). Hard disk drive with a spindle motor according to claim 16 for the rotary drive of at least one magnetic storage disk, and a writing and reading device for writing and reading data on or from the magnetic disk. Fan with a fluid dynamic bearing system according to claims 1 to 15 with a with the movable bearing component ( 12 ; 26 ) Fan wheel and an electromotive drive system ( 40 ; 42 ; 44 ) for driving the movable bearing component ( 12 ; 26 ).