DE102008033361A1 - Spindle motor for operating hard disk drive and fan, has axial section formed between outer wall of hub and inner wall of base plate or between outer wall of hub and inner wall of laminated stator core - Google Patents

Abstract

The motor (1) has a fluid-dynamic bearing system with a fixed motor component comprising a base plate (8) and a bush (3), and a rotatably movable motor component comprising a shaft pivotably supported in the bush. A hub (4) is connected with a shaft (2), and a barrier gap (10) has an axial section running parallel to rotation axes (22). The section is formed between an outer wall of the hub and an inner wall of the base plate or between an outer wall of the hub and an inner wall of a laminated stator core (15), or between an inner wall of the hub and an outer wall of the base plate.

Description

Field of the invention

The The invention relates to a spindle motor with hydrodynamic bearing system, in particular for driving a hard disk drive, a fan or The like, according to the preamble of claim 1.

Description of the state of technology

at a spindle motor with a fluid dynamic bearing is a rotatable Bearing part, for example, a cylindrical shaft, within a Drilling a fixed bearing part, for example a bearing bush, rotatably mounted. The inner diameter of the bearing bore is slight greater than the outer diameter of the shaft, so that between the lateral surfaces of bore and shaft a thin bearing gap is formed, which with a bearing fluid, preferably filled with oil.

In In many cases, the bearing bush is in a bearing seat held. To build up the fluid dynamic pressure in the bearing gap is usually at least one of the bearing surfaces of Shaft or bearing bush provided with a surface structure. Alternatively, plain bearings can be used which have no Have bearing grooves. Due to the rotational relative movement between the opposite shell or bearing surfaces arises a kind of pumping action on the bearing fluid, so that a uniform can form thick and homogeneous lubricating film, the bearing surfaces separates from each other and the fluid dynamic pressure through zones is stabilized.

One Disadvantage of fluid dynamic storage systems is that in the fluid dynamic bearings used oil over time evaporates (evaporates). In the camps must therefore be a for kept the specified life sufficient fluid supply become. This fluid supply must be greater, the higher the expected operating temperature and the required Lifespan are.

One further influencing factor on the evaporation rate of the bearing fluid is the size of the interface of the fluid to the ambient air. A small interface reduces here the fluid loss as well. Is the fluid in the storage volume in motion, because, for example, rotating parts border on the volume, so this enlarges the interface and thus the evaporation rate. Not least is the condition of the surrounding Air crucial for the evaporation rate. Is the interface surrounded by moving air, the evaporation rate is greater than at an interface which is adjacent to a relatively still, Already confined with fluid vapors enriched air volume.

• a) relativ großes Vorratsvolumen
• b) möglichst niedere Temperatur beim Vorratsvolumen
• c) kleine Grenzflächen zur Umgebungsluft
• d) weitgehend unbewegte Luft an der Grenzfläche
• e) mit Fluiddämpfen angereicherte möglichst eingeschlossene Umgebungsluft (geringer Luftaustausch mit der Umgebung)
• f) keine wesentliche Fluidbewegung im Fluidvorrat
• g) ausreichende Abdichtung des Fluid aufweisenden Lagerraumes

If a long service life at high temperatures / high speeds is required by a fluid dynamic bearing, the following requirements regarding the fluid supply must be met:

• a) relatively large storage volume
• b) lowest possible temperature in the storage volume
• c) small interfaces to the ambient air
• d) largely unmoved air at the interface
• e) ambient air enriched with fluid vapors (low air exchange with the environment)
• f) no significant fluid movement in the fluid supply
• g) adequate sealing of the fluid bearing space

JP 2006-211795 A shows a spindle motor of the type described above, in which adjacent to a horizontally extending sealing gap, which also serves as storage volume for the bearing fluid, an axially extending thin air gap is provided. The air gap forms a further sealing structure. The sealing gap and the adjacent air gap are limited by the bearing bush and the hub of the spindle motor rotating relative to the bearing bush. Due to centrifugal forces acting in the sealing gap on the bearing fluid or the fluid vapor, it comes to turbulence and a propagation of the fluid vapor radially outward, which is to be prevented by the air gap. The air gap is compared to the sealing gap only relatively short, so that leakage of fluid vapor through the air gap into the open can not be effectively prevented.

Disclosure of the invention

It Thus, it is an object of the invention to provide a hydrodynamic bearing for to develop a spindle motor to prevent leakage of bearing fluid and in particular to effectively prevent fluid vapor from the bearing, and so increase the overall life of the storage system.

These Task is by a spindle motor with fluid dynamic bearing solved with the features of claim 1.

advantageous Embodiments of the invention are in the dependent claims specified.

It is described a spindle motor with fluid dynamic bearing system, with a fixed motor component comprising a base plate and a bearing bush, and a rotary Mo a door component comprising a rotatably mounted in the bearing bushing shaft and a shaft connected to the hub, wherein between the shaft and the bearing bush a concentric bearing fluid filled with a bearing gap is provided, and facing surfaces of the bearing bush and the shaft at least one radial bearing region form, and at least one Thrust bearing region is provided, wherein the bearing gap has an open end which is sealed by a sealing gap, and adjoins the sealing gap, a barrier gap. The barrier gap has at least one axial, parallel to the axis of rotation of the motor extending portion which is formed between an outer wall of the hub and an inner wall of the base plate or between an outer wall of the hub and an inner wall of a stator lamination or between an inner wall of the hub and an outer wall of the baseplate.

From evaporates the surface of the bearing fluid in the sealing gap constantly bearing fluid, the more, the higher the temperature of the bearing fluid and the larger its surface area is. This fluid vapor can then pass through an air gap escape the atmosphere outside the camp and condense inside the engine. The air gap is located usually between a fixed surface of the bearing bush and a rotating surface of the hub, so that in particular in radially extending sections of the air gap an air vortex forms due to the centrifugal forces, the act on the air or the fluid vapor. This air vortex transports the fluid vapor in the direction radially outward and over the air gap in the outside atmosphere.

According to the invention now a barrier gap provided, preferably as part of the original Air gap whose gap distance is very small and its axial Length parallel to the axis of rotation, as large as possible. Due to the small gap width and the large axial length of the barrier gap can be in the area of the barrier gap no Air vortex form more, and because of the small cross section and the comparatively long length of the barrier gap hardly any fluid vapor can leave the barrier gap to the outside. Consequently the storage system according to the invention has hardly any fluid losses in the form of evaporating bearing fluid, so that in particular a long life of the storage system can be guaranteed and / or a smaller volume of fluid is provided within the capillary seal of the bearing can be. In particular, the axial section of the barrier gap acts as an effective barrier against leakage of fluid vapor, as in the axial Section no centrifugal forces in the direction of the longitudinal extent the gap portion act and thus the smallest possible Transport of fluid vapor takes place in the axial direction.

According to one first embodiment of the invention, the barrier gap between facing each other and relatively movable surfaces the bushing and the hub is formed and extends substantially axially and parallel to the axis of rotation of the bearing. This embodiment is especially suitable for engines according to the so-called Single plate design, where at the bottom of the shaft is a pressure plate is formed, which forms the or the thrust bearing and the storage volume formed in the form of a capillary seal at the open end of the bearing gap is. Another, axially extending portion of the barrier gap is located between the stator pack and the hub. The two Portions of the barrier gap are defined by a radially extending Air gap connected together.

In In another embodiment of the invention, the barrier gap between facing and relatively movable surfaces be formed of the base plate and the hub. This embodiment is particularly suitable for so-called Top Thrust bearings, in which the thrust bearing between an end face of the Bearing bush and a lower surface of the hub is formed. In these spindle motors, the sealing gap and extend the storage volume in the axial direction outside of the thrust bearing, so that the barrier gap must be provided elsewhere, as the single plate design. In this embodiment, the barrier gap as a labyrinth gap between the edge of the hub and an annular groove formed of the base plate and appears in cross-section approximately U-shaped. Here, the barrier gap has an axially extending section on, passing through an outer peripheral surface the hub and an inner peripheral surface of the base plate is limited. In a modified embodiment, the barrier gap have a further axially extending portion through an outer peripheral surface of the base plate and an inner peripheral surface of the hub is limited. Between the two axially extending portions of the barrier gap is a radially extending air gap provided by an annular Front of the hub and an opposite surface the base plate is limited. However, this contributes only slightly to reduce the air exchange at.

In another embodiment of the invention, the barrier gap is formed between mutually facing and relatively movable surfaces of the hub and a stator arrangement arranged on the base plate. The barrier gap in this case has an axially extending portion, which is delimited by an outer peripheral surface of the hub and an inner peripheral surface of the stator assembly. The end face of the hub forms with the base plate a radially extending air gap, the connects the sealing gap with the barrier gap.

Of the Barrier gap forms together with a radially extending air gap a connection between the sealing gap of the storage system and the Outside atmosphere, especially one in the spindle motor arranged stator space. Here is the actual barrier gap arranged parallel to the axis of rotation and the connecting air gap transverse or perpendicular to the axis of rotation.

The Slit width of the barrier gap is as small as possible, preferably less than or equal to 50 microns and its length as possible large, preferably greater than 0.5 mm.

The The invention will be explained in more detail below with reference to the drawings which describes further features and advantages of the invention devoted.

Brief description of the drawings

1 shows a schematic sectional view of a first embodiment of a spindle motor according to the invention with bottom mounted thrust bearing.

2 shows a schematic sectional view of a second embodiment of a spindle motor according to the invention with top mounted thrust bearing.

3 shows a schematic sectional view of a third embodiment of a spindle motor according to the invention with top mounted thrust bearing.

4 shows a schematic sectional view of a fourth embodiment of a spindle motor according to the invention with top mounted thrust bearing.

Description of preferred Embodiments of the invention

The drawings show spindle motors 1 for driving a hard disk drive, fan or the like, with a hydrodynamic bearing system according to the invention. In the examples shown, one is the hub 4 bearing wave 2 rotatable in a fixed bearing bush 3 stored. Of course, the invention also includes constructions in which a fixed shaft 2 from one of the hub 4 carrying, rotatable bearing bush 3 is surrounded.

The in 1 shown spindle motor 1 has a fixed base plate 8th on, in which the bearing bush 3 is held. The bearing bush 3 has an axial cylindrical bore, in which the shaft 2 rotatable to form a bearing gap filled with a bearing fluid 17 is included. The free end of the shaft 2 carries a hub 4 on which one or more storage disks (not shown) of a hard disk drive or a fan wheel (not shown) of a fan are arranged and fastened.

As it turned out 1 results, the bearing bush points 3 at its upwardly open end of a roughly conical cross-section cavity, which widens radially outward. The cavity forms a sealing gap 9 and acts as a capillary seal and also serves as storage and compensation volume for the bearing fluid. The sealing gap 9 adjoins directly to the bearing gap 17 and seals it to the outside.

The hydrodynamic bearing arrangement is characterized by two radial bearing areas 18 . 19 formed, which are characterized by a groove pattern on the surface of the shaft 2 and / or on the inner surface of the bearing bush 3 is provided. Once the wave 4 is set in rotation, builds due to the groove pattern hydrodynamic pressure in the bearing gap 17 or in the bearing fluid contained therein, so that the bearing is sustainable.

A pressure plate arranged at the lower end of the shaft 13 forms with the cover plate 14 a so-called hydrodynamic thrust bearing at the lower end of the shaft 2 from and absorbs the axial forces of the bearing assembly. This thrust bearing area is through the cover plate 14 hermetically sealed, so that no bearing fluid from the bearing gap 17 can escape.

On a radially inner surface of the hub 4 is an annular permanent magnet 5 arranged with a plurality of pole pairs of the spaced over a working air gap stator assembly 6 be subjected to an alternating electric field, so that the hub 4 together with the wave 2 is set in rotation. The power supply of the stator windings, for example, via electrical contacts 21 ,

The sealing gap 9 is connected via an air gap with the outside environment. The air gap initially extends horizontally between the end face of the bearing bush 3 and an opposite surface of the hub 4 , and then goes into a vertical section 10 over, extending between an outer circumference of the bearing bush 3 and an opposite inner peripheral surface of the hub 4 extends. From the sealing gap 9 continuously evaporate small amounts of bearing fluid, which accumulated in engines of known design in the air gap and formed turbulence due to the centrifugal forces, so that fluid vapor over the Air gap could escape to the outside.

According to the invention, the air gap, in particular an axial section of the air gap, as a barrier gap 10 formed, which has a small gap width of preferably less than 150 microns and has the largest possible axial length. Another axially extending portion of the barrier gap 10 ' is located between an outer wall of the hub 4 as well as the stator lamination stack 15 , One the two axial sections of the barrier gap 10 . 10 ' connecting and radially extending air gap 12 does not contribute to the reduction of air exchange. The barrier gap 10 ' is with the stator space 20 of the engine and thus connected to the outside environment. The barrier gap 10 . 10 ' forms a barrier to the fluid vapor that accumulates in the radial portion of the air gap adjacent the seal gap. Due to the no gap width of the barrier gap 10 . 10 ' and its large length can only very little fluid vapor over the barrier gap in the stator space 20 and thus escape the environment.

The spindle motor according to 2 differs in structure from the spindle motor according to 1 especially in that at the lower end of the shaft 102 no pressure plate is present, which forms the thrust bearing, but an upper thrust bearing 116 between the front of the bearing bush 103 and a bottom of the hub 104 is formed. The thrust bearing 116 extends transversely to the axis of rotation 122 and flows into a sealing gap 109 , the first radial but mostly axial, that is parallel to the axis of rotation 122 runs and is limited by an outer circumference of the bearing bush 103 and an inner circumference of the hub 104 , The sealing gap 109 is partially filled with bearing fluid and with the bearing gap 117 connected. At the bottom of the shaft is a stopper flange 113 provided, which prevents falling out of the shaft from the bearing bush by being at an edge of the bearing bush 103 strikes. The lower part of the bearing, which is covered by a cover 114 is covered by a recirculation channel 111 with a radially outer portion of the thrust bearing 116 connected and serves as a fluid reservoir and allows circulation of the bearing fluid in the storage system. Beyond the sealing gap 109 is now according to the invention a barrier gap 110 . 110 ' provided, which is formed by the open edge of the hub 104 which is in a U-shaped recess of the base plate 108 is arranged. The barrier gap comprises two axially extending sections 110 . 110 ' each between the cylindrical surfaces of the hub 104 and the opposing surfaces of the base plate 108 , The radial air gap 112 formed between the end face of the hub 104 and an opposite surface of the base plate 108 connects both axially extending sections 110 of the barrier gap, but does not itself contribute to the reduction of air exchange. The barrier gap 110 . 110 ' is thus nested U-shaped and has the largest possible axial length. On the other hand, however, the smallest gap width of the barrier gap 110 . 110 ' as low as possible, so that in the sealing gap 109 located fluid vapor difficult over the labyrinth structure of the barrier gap 110 . 110 ' or the air gap 112 to the outside, that is in the stator space 120 can penetrate.

3 shows a spindle motor, which also has a top thrust design and is designed similar to the spindle motor 2 , Identical components or components with the same functions are provided with the same reference numerals.

Again, at the open end of the sealing gap 109 in the axial direction approximately parallel to the axis of rotation 122 extends, a vertical barrier gap 110 provided, which is approximately parallel to the axis of rotation 122 extending section exists. The sealing gap 109 is through a radially extending air gap 112 with the barrier gap 110 connected. The axial section of the barrier gap 110 is limited by the outer circumference of the rim of the hub 104 and the laminated core 115 of the stator 106 , The barrier gap 110 then flows into the Statorraum 120 , Also this barrier gap 110 prevents leakage of fluid vapor from the sealing gap 109 in the stator room 120 and thus in the outer area of the camp. Because the stator 106 firmly in the base plate 108 is arranged, the gap distance of the axial section 110 the barrier gap set very accurately and kept small, preferably smaller than 50 microns.

4 shows a further embodiment of a spindle motor with the features of the spindle motors according to the 2 and 3 , wherein like components with the same reference numerals as in the 2 and 3 are designated.

Beyond the sealing gap 109 borders a radially extending air gap 112 on, in the inventive and axially extending barrier gap 110 passes. The barrier gap 110 includes a very narrow axial section 110 which is formed from the outer edge of the hub 104 and an inner edge of a finger-like portion of the base plate 108 , on the outside of the stator lamination 115 is arranged. The axially extending section 110 of the barrier gap 110 flows into the stator chamber 120 and effectively prevents diffusion of fluid vapor from the seal gap 109 in the stator room 120 ,

1

spindle motor

2

wave

3

bearing bush

4

hub

5

magnet

6

stator

7

yoke

8th

baseplate

9

seal gap

10

Barrier gap, vertical 10 '

11

12

Air gap, horizontal

13

printing plate

14

cover

15

stator lamination

16

17

bearing gap

18

Radial bearing region

19

Radial bearing region

20

stator

21

Contacts, electrical

22

axis of rotation

101

spindle motor

102

wave

103

bearing bush

104

hub

105

magnet

106

stator

107

yoke

108

baseplate

109

seal gap

110

Barrier gap, vertical 110 '

111

recirculation

112

Air gap, horizontal

113

Stopperflansch

114

cover

115

stator lamination

116

axial bearing

117

bearing gap

118

Radial bearing region

119

Radial bearing region

120

stator

121

Contacts, electrical

122

axis of rotation

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 2006-211795 A [0007]

Claims (11)

Spindle motor ( 1 ; 101 ) with fluid dynamic bearing system, with a fixed motor component comprising a base plate ( 8th ; 108 ) and a bearing bush ( 3 ; 103 ), and one around a rotation axis ( 22 ; 122 ) rotatable motor component comprising a rotatably mounted in the bearing bush shaft ( 2 ; 102 ) and a hub connected to the shaft ( 4 ; 104 ), whereby between the wave ( 2 ; 102 ) and the bearing bush ( 3 ; 103 ) a concentric bearing gap filled with a bearing fluid ( 17 ; 117 ) is provided, and facing surfaces of the bearing bush ( 3 ; 103 ) and the wave ( 2 ; 102 ) at least one radial bearing area ( 18 . 19 ; 118 . 119 ) and at least one thrust bearing region ( 116 ), wherein the bearing gap has an open end which is penetrated by a sealing gap ( 9 ; 109 ) is sealed, and at the sealing gap a barrier gap ( 10 ; 110 ), characterized in that the barrier gap ( 10 . 10 '; 110 . 110 ' ) at least one axially, parallel to the axis of rotation ( 22 ; 122 ) extending portion which is formed between an outer wall of the hub ( 4 ; 104 ) and an inner wall of the base plate ( 8th ; 108 ) or between an outer wall of the hub ( 4 ; 104 ) and an inner wall of a laminated stator core ( 15 ; 115 ) or between an inner wall of the hub ( 4 ; 104 ) and an outer wall of the base plate ( 8th ; 108 ). Spindle motor according to claim 1, characterized in that the sealing gap ( 9 ; 109 ) is at least partially filled with bearing fluid and the barrier gap ( 10 . 10 '; 110 . 110 ' ) is free from liquid bearing fluid. Spindle motor according to one of claims 1 or 2, characterized in that a portion of the barrier gap ( 10 ) between facing and relatively movable surfaces of the bearing bush ( 3 ) and the hub ( 4 ) is trained. Spindle motor according to claim 3, characterized in that the section ( 10 ) of the barrier gap between the bushing ( 3 ) and the hub ( 4 ) substantially parallel to the axis of rotation ( 22 ) of the bearing extends. Spindle motor according to claim 5, characterized in that the barrier gap has a first axially extending section (FIG. 110 ) formed by an outer peripheral surface of the base plate ( 108 ) and an inner peripheral surface of the hub ( 104 ) is limited, and a second axially extending portion ( 110 ' ), which by an outer peripheral surface of the hub ( 104 ) and an inner peripheral surface of the base plate ( 108 ) is limited. Spindle motor according to one of claims 1 or 2, characterized in that the barrier gap ( 110 . 110 ' ) between mutually facing and relatively movable surfaces of the base plate ( 108 ) and the hub ( 104 ) and the hub ( 104 ) and arranged on the base plate stator assembly ( 115 ) is trained. Spindle motor according to claim 8 or 9, characterized in that at least a portion of the barrier gap ( 10 . 10 '; 110 . 110 ) a radial axis of rotation ( 22 ; 122 ) running air gap ( 12 ; 112 ) bordered by an annular end face of the hub ( 4 ; 104 ) and an opposite surface of the base plate ( 8th ; 108 ) is formed. Spindle motor according to one of claims 1 to 10, characterized in that the sealing gap ( 9 ; 109 ) through the barrier gap ( 10 . 10 '; 110 . 110 ' ) and the air gap ( 12 ; 112 ) with a stator space arranged in the spindle motor ( 20 ; 120 ) connected is. Spindle motor according to one of claims 1 to 11, characterized in that the barrier gap ( 10 . 10 '; 110 . 110 ' ) preferably parallel to the axis of rotation ( 22 ; 122 ) of the spindle motor is arranged. Spindle motor according to one of claims 1 to 12, characterized in that the gap width of the barrier gap ( 10 . 10 '; 110 . 110 ' ) is less than 50 microns. Spindle motor according to one of claims 1 to 13, characterized in that the length of the barrier gap ( 10 . 10 '; 110 . 110 ' ) is greater than or equal to 0.5 mm.