DE102010056251A1 - Fluid bearing for spindle motor, has shaft that is rotatably mounted in relative to bearing bush by fluid dynamic radial bearing and hydrostatic thrust bearing about rotation axis - Google Patents

Abstract

The fluid bearing has a shaft (12), fixed element and bearing bush (10). The shaft is disconnected by a radial bearing gap (14) filled with bearing fluid in bearing bore of the bearing bush. The shaft is rotatably mounted in relative to the bearing bush by fluid dynamic radial bearing (20,22) and hydrostatic thrust bearing (26) about a rotation axis (52). An independent claim is included for spindle motor.

Description

Field of the invention

The invention relates to a fluid bearing, in particular for the rotary mounting of a spindle motor, with a rotating component and a stationary component, which are rotatably supported relative to each other by means of a fluid dynamic radial bearing and a thrust bearing.

Description of the Prior Art

From the prior art, in particular by the applicant itself, a variety of fluid bearings of various types is known.

The DE 10 2005 019 944 B3 or the DE 103 45 907 B4 Disclose, for example spindle motors with a fluid dynamic bearing system with a fixed bearing bush in which a shaft is rotatably mounted. The pivot bearing takes place by means of two fluid dynamic radial bearings spaced apart from one another and two fluid-dynamic axial bearings which are formed on a pressure plate which is connected to the shaft. The relatively rotatable bearing components are separated by a bearing gap of a few micrometers width, which is filled with a bearing fluid. Upon relative rotation of the bearing components, bearing groove structures applied to the bearing surfaces create a fluid dynamic pressure in the bearing fluid which renders the bearing system viable.

Since the bearing gap is very narrow, the bearing fluid generates a significant bearing friction due to its relatively high viscosity, which is responsible for the majority of the energy consumption of the spindle motor in the rotary bearing of a spindle motor. Especially in mobile devices, but also in servers in which spindle motors are used for example for driving hard disk drives, a power-saving operation is of great importance.

Disclosure of the invention

It is the object of the invention to provide a fluid bearing, which has a significantly lower bearing friction compared to a fluid dynamic bearing system described above. A spindle motor with such a fluid bearing will also be described.

The fluid bearing consists of a rotating component comprising a shaft and a stationary component comprising a bearing bush, wherein the shaft is received in a bearing bore of the bearing bush and separated therefrom by a bearing with a bearing fluid radial bearing gap, wherein the shaft relative to the bearing bush by means of fluid dynamic radial bearings and a thrust bearing is rotatably mounted.

According to the invention, the thrust bearing is designed as a hydrostatic thrust bearing.

Along the radial bearing gap which extends between the shaft and the bearing bush, two radial bearings are preferably arranged, namely a first radial bearing and a second radial bearing arranged at an axial distance therefrom. Between the two radial bearings a Separatorspalt is provided with a significantly larger gap width compared to the radial bearing gap.

The first, the bearing opening adjacent radial bearing of the fluid bearing pumps the bearing fluid located in the radial bearing gap into the camp, d. H. the first radial bearing comprises asymmetric radial bearing grooves which generate a pumping action on the bearing fluid in the radial bearing gap, which is directed predominantly in the direction of the separator gap. Due to this pumping action, a higher pressure prevails in the separator gap than the atmospheric pressure. This increased pressure can be exploited to create a defined flow of bearing fluid through the bearing gap. According to the invention, this pumping function is also used to generate the hydrostatic pressure required for the thrust bearing.

The second radial bearing also includes radial bearing grooves that create a pumping action on the bearing fluid in the radial bearing gap. The radial bearing grooves may be formed symmetrically, d. H. generate an equally large pumping action on the bearing fluid in both directions of the bearing gap. In order to further increase the pressure in the separator gap, the second radial bearing can alternatively also be provided with asymmetrical radial bearing grooves, which generate a predominant pumping action in the direction of the separator gap.

The bearing bore is closed on one side by a closure plate. The thrust bearing formed along a thrust bearing gap is provided between an end face of the shaft and the shutter plate. According to the invention, the thrust bearing does not comprise bearing groove structures, since here no fluid-dynamic pressure has to be generated, but rather a hydrostatic pressure is generated which applies the axial bearing force.

To generate this hydrostatic pressure in the axial bearing gap, a bore is provided in the shaft, which connects the separator gap with the axial bearing gap. Due to the targeted pumping action of the radial bearing grooves in the direction of the separator gap, an overpressure is generated in the separator gap, the is transmitted through the bore of the shaft in the axial bearing gap and makes the thrust bearing load-bearing.

For better utilization of this hydrostatic pressure, a hydrostatic bearing pocket can be introduced in the region of the axial bearing gap either in the closure plate or the end face of the shaft, wherein the bore of the shaft opens into this bearing pocket and a bearing fluid pressure is established there.

The bearing fluid can circulate through the bearing in various ways. As in a fluid dynamic bearing known from the prior art, the bearing fluid pumped from the first radial bearing in the direction of the separator gap can pass through the second radial bearing and flow back to the first bearing via a recirculation bore within the bearing bush. By inventively proposed new bore in the shaft, which connects the Separatorspalt with the Axiallagerspalt or a storage bag, the bearing fluid can now pass directly from the first radial bearing in the bearing pocket. The pressure in this storage bag then corresponds approximately to the pressure within the Separatorspalts between the two radial bearings. This pressure in turn raises the shaft, in which case the bearing fluid can then flow off through a gap formed at the edge of the bearing pocket, preferably via a recirculation bore additionally provided in the bearing bush.

An axial preload for the hydrostatic thrust bearing can be generated for example by the electro-magnetic drive system of the spindle motor having this fluid bearing. It then sets a balance between the hydrostatic thrust bearing and the magnetic thrust bearing for generating an axial biasing force. This magnetic thrust bearing can be formed, for example, in that the rotor magnet is arranged offset in the axial direction relative to the stator arrangement in the axial direction, whereby a force directed axially downward in the direction of the base plate is produced on the hub. Alternatively or additionally, an arranged on the base plate axially below the rotor magnet ferromagnetic tension ring can be provided which also exerts an axially downward force on the hub.

Since the gap of the bearing pocket of the hydrostatic thrust bearing is much larger than the necessary for a fluid dynamic thrust bearing gap, in particular reduces the bearing friction of the fluid bearing and thus the power consumption of the spindle motor. Spindle motors used to drive 2.5-inch hard disk drives saw a 10 percent reduction in bearing friction.

On a front side of the bearing bush, a cover may be provided which surrounds the bearing bush partially and is cup-shaped. This cover, together with an outer surface of the bearing bush, partially filled with bearing fluid fluid reservoir which is connected to the bearing gap and tapers in the direction of the bearing gap.

The invention also relates to a spindle motor with a fluid bearing described above, in particular for the drive of storage disks in hard disk drives.

The invention will be explained in more detail with reference to drawing figures, resulting in the description of the drawings further features and other advantages.

Brief description of the drawings

1 : shows a section through a spindle motor with a fluid bearing according to the invention.

2 1 shows schematically a view of the shaft with two asymmetric radial bearings, both pumping in the direction of the other radial bearing.

Description of preferred embodiments of the invention

1 shows a section through a spindle motor according to the invention. The spindle motor includes a fixed base plate 42 , wherein a bearing bush 10 in a recess of the base plate 42 is attached. The bearing bush 10 has a cylindrical bearing bore, in which a shaft 12 is received rotatably. The diameter of the bearing bore is slightly larger than the diameter of the shaft 12 , so between the shaft 12 and the bearing bore a radial bearing gap 14 of a few microns width remains. One end of the bearing bore is through a closure plate 18 hermetically sealed. The radial bearing gap 14 is filled with a bearing fluid and goes in the direction of the closure plate 18 in a thrust bearing gap 28 above. The thrust bearing gap is through the closure plate 18 and a stopper ring 16 limited at one end of the shaft 12 is arranged on the closed side of the bearing. The stopper ring 16 is preferably integral with the shaft 12 formed and in a corresponding recess of the bearing bush 10 arranged. This stopper ring 16 prevents the shaft from falling out 12 from the bearing bore of the bearing bush 10 ,

Along the radial bearing gap 14 are two radial bearings 20 . 22 arranged at an axial distance from each other. The radial bearings 20 . 22 are characterized by radial bearing grooves, which are either on the surface of the shaft 12 or the surface of the bearing bore of the bearing bush 10 are arranged. These radial bearing grooves have for example a herringbone or sinusoidal shape, which may be symmetrical but also asymmetric. The first radial bearing 20 preferably has asymmetrical radial bearing grooves, which the bearing fluid in the direction of the second radial bearing 22 pump while the second radial bearing 22 preferably has symmetrical radial bearing grooves, but may also be formed asymmetrically and in the latter case, a pumping action in the direction of the first radial bearing exerts. With a rotation of the shaft 12 in the bearing bore generate the radial bearing grooves of the two radial bearings 20 . 22 a pumping action on the bearing fluid, so that builds up a hydrodynamic pressure in the bearing gap. The first radial bearing 20 is formed asymmetrically and has longer branches and shorter branches on which the bearing fluid in different directions of the radial bearing gap 14 pump. The longer branches of the radial bearing grooves of the first radial bearing 20 generate a stronger pumping action than the shorter branches, leaving the first radial bearing 20 mainly in the direction of the second radial bearing 22 inflated. The second radial bearing 22 is through a separator gap 24 from the first radial bearing 20 separated. The separator gap 24 is one opposite the radial bearing gap 14 common section of the bearing gap. The second radial bearing 22 generated by its symmetrical radial bearing grooves a non-directed pumping action.

Between the bottom of the shaft 12 or the bottom of the stop locking 16 and the inner surface of the closure plate 18 runs the thrust bearing gap 28 , in whose area a hydrostatic thrust bearing 26 is formed. The two radial bearings 20 . 22 are fluid dynamic bearings, ie the bearing force is generated by forming a fluid dynamic pressure by the rotation of the bearing components. The thrust bearing 26 is inventively designed as a hydrostatic bearing, ie the thrust bearing 26 has no active hydrodynamic bearing structures that produce a hydrodynamic pressure. Instead, the thrust bearing includes 26 preferably a storage bag 30 , for example, as a recess at the bottom of the shaft 12 or alternatively in the top of the closure plate 18 is formed. In order to achieve a rapid lifting of the shaft during start-up of the engine, in the area of the small thrust bearing gap in the outer periphery of the bottom of the shaft 12 or in the opposite surface of the closure plate 18 flat spiral groove-shaped thrust bearing structures are provided. In the storage bag 30 opens a hole 32 whose other end into the Separatorspalt 24 empties. As shown, this hole can be centered to the axis of rotation 52 of the warehouse in the storage bag 30 open, but it is also possible to provide the lower end of the bore acentric to avoid or at least reduce an imbalance of the shaft. By the pumping action of the first radial bearing 20 in the direction of the separator gap 24 forms in the separator gap 24 a high pressure over the hole 32 in the area of the storage bag 30 of the hydrostatic thrust bearing 26 is transmitted. This pressure causes the thrust bearing 26 stable, once in the separator gap 24 a sufficiently high pressure prevails. The hydrostatic pressure in the thrust bearing 26 is thus dependent on the pressure in the separator gap 24 passing through the first hydrodynamic radial bearing 20 or the first and second hydrodynamic radial bearings 20 . 22 is produced.

When the storage system is at a standstill, the bottom of the shaft lies on the closure plate 18 on. As soon as the bearing system is set in rotation, the radial bearing builds up in the separator gap due to the hydrodynamic effect 20 . 22 hydrodynamic pressure very quickly. The pressure is over the hole 32 passed as hydrostatic pressure in the bearing pocket and ensures that the bottom of the shaft 12 even at relatively low speeds of the shutter plate 18 takes off. This reduces the wear in the thrust bearing during start and stop operation of the bearing.

The one in the storage bag 30 Existing hydrostatic pressure may be present laterally in the area of the stopper ring 16 drain and passes through one in the bearing bush 10 arranged recirculation bore 34 back into the cycle, ie in the area of the upper first radial bearing 20 , The recirculation bore 34 leads to a fluid reservoir 38 that is formed between an outer circumference of the bearing bush 10 and a cover over it 36 , The fluid reservoir 38 is directly with the radial bearing gap 14 connected and serves as a compensating volume, for example, at temperature expansion of the bearing fluid and additionally as a consumption reservoir. The fluid reservoir 38 tapers conically towards the radial bearing gap 14 , wherein the bearing fluid is held in the reservoir by capillary forces, ie, the fluid reservoir also serves as a capillary seal for the open end of the radial bearing gap 14 , In the example shown, the fluid reservoir 38 formed angled, ie it runs partially perpendicular to the axis of rotation 52 and partially parallel to the axis of rotation 52 ,

A hub 40 forms the rotor of the spindle motor. The hub 40 is fixedly connected to the free end of the shaft and is driven in rotation by an electromagnetic drive system. The drive system consists of a stator arrangement 44 , which is fixed to the base plate. The hub 40 is cup-shaped and covers the stator assembly 44 partially. The hub 40 has an outer edge, on the inner Lateral surface of a rotor magnet 46 is arranged, the radially opposite the stator assembly 44 at the hub 40 is attached. By appropriate energization of the stator 44 be the rotor magnet and thus the hub 40 set in rotation.

The hydrostatic thrust bearing 26 exercises on the arrangement of shaft 12 and hub 40 a force coming from the thrust bearing 26 seen from axially upward in the direction of the hub 40 is directed. The hydrostatic thrust bearing 26 acts against a magnetic thrust bearing and stabilizes the rotor assembly in the axial direction. The magnetic thrust bearing is formed by a pull ring 48 that is axially below the rotor magnet 46 is arranged and from the rotor magnet 46 magnetically attracted. This magnetic force between the rotor magnet 46 and the pull ring 48 acts opposite to the bearing force of the thrust bearing 26 and keeps the bearing assembly in axial balance. The energization with the stator arrangement 44 takes place for example via a contact 50 on the base plate 42 , Alternatively or additionally, the rotor magnet 46 from its magnetic center position in the axial direction upward relative to the stator assembly 46 arranged offset, whereby an axially downward force is exerted on the hub.

2 schematically shows a wave 112 as they also for example in the camp 1 can be used. On the shaft are radial bearing grooves of a first radial bearing 120 and a second radial bearing 122 arranged. Unlike the radial bearings of 1 is the second radial bearing 122 not symmetrical but also asymmetrical as the first radial bearing 120 , Both radial bearings 120 . 122 practice on the in the bearing gap ( 1 ) located bearing fluid from a pumping action, which is directed against each other, so that in the separator gap 24 a high pressure is achieved, which is then used to generate the hydrostatic force for the thrust bearing 28 is used.

LIST OF REFERENCE NUMBERS

10

bearing bush

12

wave

14

Radial bearing gap

16

stopper ring

18

closing plate

20

radial bearings

22

radial bearings

24

separator gap

26

thrust

28

thrust bearing

30

bearing pocket

32

drilling

34

Rezirkulationsbohrung

36

cover

38

fluid reservoir

40

hub

42

baseplate

44

stator

46

rotor magnet

48

pull ring

50

contact

52

axis of rotation

112

wave

120

radial bearings

122

radial bearings

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005019944 B3 [0003]
• DE 10345907 B4 [0003]

Claims (10)

Fluid bearing, in particular for a spindle motor, with a rotating component, comprising a shaft ( 12 ; 112 ), and with a fixed component comprising a bearing bush ( 10 ), wherein the shaft in a bearing bore of the bearing bush ( 10 ) and from this by a filled with a bearing fluid radial bearing gap ( 14 ) is separated, the shaft ( 12 ) relative to the bearing bush by means of fluid dynamic radial bearings ( 20 . 22 ; 120 . 122 ) and a thrust bearing ( 26 ) about a rotation axis ( 52 ) Is rotatably mounted, characterized in that the thrust bearing ( 26 ) is a hydrostatic thrust bearing. Fluid bearing according to claim 1, characterized in that along the radial bearing gap ( 14 ) a first radial bearing ( 20 ; 120 ) and at an axial distance a second radial bearing ( 22 ; 122 ) and that between the two radial bearings ( 20 . 22 ; 120 . 122 ) a separator gap ( 24 ) with a comparison with the radial bearing gap ( 14 ) enlarged gap width is provided and that the first radial bearing ( 20 ; 120 ) has asymmetric radial bearing grooves, which have a pumping action on the in the radial bearing gap ( 14 ) generate bearing fluid, the pumping action predominantly in the direction of the Separatorspalts ( 24 ). Fluid bearing according to one of claims 1 to 2, characterized in that the second radial bearing ( 122 ) Has radial bearing grooves, which have a pumping action on the in the radial bearing gap ( 14 ) and that the second radial bearing ( 122 ) asymmetric radial bearing grooves whose pumping action predominantly in the direction of the Separatorspalts ( 24 ). Fluid bearing according to one of claims 1 to 3, characterized in that the bearing bore of the bearing bush ( 10 ) on one side by a closure plate ( 18 ) and that the thrust bearing ( 26 ) between an end face of the shaft ( 12 ) and the closure plate ( 18 ) is arranged and a thrust bearing gap ( 28 ) having. Fluid bearing according to one of claims 1 to 4, characterized in that in the shaft ( 12 ; 112 ) a hole ( 32 ), which separates the separator gap ( 24 ) with the axial bearing gap ( 28 ) connects. Fluid bearing according to one of claims 1 to 5, characterized in that in the region of the axial bearing gap ( 28 ) in the closure plate ( 18 ) and / or the end face of the shaft ( 12 ) or a stop ring connected to the shaft ( 16 ) a storage bag ( 30 ) is introduced. Fluid bearing according to one of claims 1 to 6, characterized in that at one end face of the bearing bush ( 10 ) a cover ( 36 ) is provided, which the bearing bush ( 10 ) and that between an outer surface of the bearing bush ( 10 ) and an inner surface of the cover ( 36 ) at least partially filled with bearing fluid fluid reservoir ( 38 ) is formed and that the fluid reservoir ( 38 ) with the radial bearing gap ( 14 ) and in the direction of the radial bearing gap ( 14 ) rejuvenated. Fluid bearing according to claim 7, characterized in that the cover ( 36 ) is cup-shaped. Fluid bearing according to one of claims 1 to 8, characterized in that a recirculation channel ( 34 ) within the bearing bush ( 10 ) passing the fluid reservoir ( 38 ) with an area at the radial outer edge of the lower end of the shaft ( 12 . 112 ) connects. Spindle motor with a fluid bearing, in particular for driving storage disks in hard disk drives, with a base plate ( 42 ), one related to the base plate ( 42 ) fixed stator arrangement ( 44 ), a fixed bearing component ( 10 ), one by means of the fluid bearing in the fixed bearing component ( 10 ) rotatably mounted shaft ( 12 ) and one with the shaft ( 12 ), rotationally driven hub ( 40 ), characterized in that the fluid bearing fluid dynamic radial bearings ( 20 . 22 ; 120 . 122 ) and a hydrostatic thrust bearing ( 26 ).

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