DE102006020408B4 - Sealing arrangement for a fluid bearing - Google Patents

Abstract

A sealing arrangement for a fluid bearing with a bearing component (12) and a relative to this about a rotation axis (30) rotating bearing member (10), wherein the two bearing components are spaced by a bearing fluid filled with a bearing gap (16), wherein the bearing gap at least one having a sealed end sealed by a capillary seal and a pumping seal is provided, wherein the capillary seal between the bearing gap (16) and the pumping seal is arranged, characterized in that the one bearing member (10) comprises an annular pressure plate (14), and the capillary between an outer periphery of the pressure plate (14) and the other bearing member (12) is arranged.

Description

Field of the invention

The invention relates to the field of fluid dynamic bearing systems and more particularly to a sealing arrangement for a fluid bearing according to the preamble of the independent claims. Such fluid bearings are used for example in spindle motors.

State of the art

For spindle motors with hydrodynamic bearing systems (fluid bearings) preferably used seal types are passive, straight or tapered capillary seals with a large reservoir volume for the bearing fluid or active, with suitable pump structures, eg. As obliquely mounted grooves provided gap seals virtually no reservoir volume.

The US 5 018 880 A shows a fluid bearing, which has a recess as a reservoir for the bearing fluid and arranged at the open end of the bearing gap pump structure. The pumping structure is formed by grooves, which can be arranged on the surface of the shaft or the inside of the shaft receptacle and convey back out of the reservoir to the outside escaping bearing fluid back into the recess. The sealing effect is based exclusively on the pump seal.

For the future, new, robust and easy-to-manufacture sealing concepts are necessary for z. For example, spindle motors used in hard disks with ever higher vibration requirements (shock resistance of, for example, greater than 1000 times the acceleration due to gravity) or smaller sizes (and thus dimensions available for sealing).

In addition, for new engine concepts (eg, a motor with an additional top-mounted, ie stationary shaft and therefore a bearing system open on two sides), further possibilities for sealing the bearing system are desirable in order to achieve greater design freedom.

Another issue is the reduction of oil evaporation, not only to increase the life of the storage system and therefore the entire engine, but also to minimize or eliminate contamination of the storage media against a background of ever-increasing storage densities and improved, more sensitive storage techniques. In addition, there is a correspondingly lower oil volume in the increasingly smaller fluid bearings.

The DE 695 13 473 T2 discloses a hydrodynamic bearing with a seal assembly, which has one or more Kapillardichtungen, preferably conical Kapillardichtungen to seal the bearing gap. 3 shows a seal assembly with a capillary seal, which adjoins the bearing gap and a region whose surfaces are coated with a barrier film to prevent wetting with lubricant. A pumping seal with arranged on the sealing surfaces pump structures is not disclosed.

The US Pat. No. 6,787,954 B2 shows a tapered seal assembly, wherein no pumping seal is disclosed, which is characterized by pumping structures.

The US 2005/0058373 A1 revealed in 1 a fluid dynamic bearing with a sealing arrangement, wherein the bearing gap is sealed on one side by a capillary seal, and on the other side by a pumping seal. However, no additional capillary seal is provided on the pump seal side.

The US 5 850 318 A discloses a fluid bearing wherein a capillary seal combined with a pumping seal is neither designated nor described.

Disclosure of the invention

It is the object of the invention to provide a seal assembly for fluid bearing, which has a simple construction and yet is effective even at high shock load and reduces the oil evaporation in the storage system.

This object is solved by a sealing arrangement as stated in the independent claims.

Preferred embodiments and further developments of the invention are specified in the dependent claims, to the disclosure of which reference is made at this point.

According to the invention, a fluid bearing comprising the sealing arrangement comprises a stationary bearing component and a bearing component which rotates about a rotational axis relative thereto, wherein the bearing components are spaced apart from one another by a bearing gap filled with a bearing fluid. The bearing gap has at least one open end sealed off by means of a capillary seal, and a pumping seal is provided, wherein the capillary seal is arranged between the bearing gap and the pumping seal.

The clever combination of the properties of the two mentioned seal variants of capillary seal and pump seal in a novel type of seal gives the advantages of both variants, namely a seal with a large reservoir volume and at the same time much greater safety / stiffness against shocks compared to conventional seals with large volume and even active gap seals.

The invention provides for a fluid-dynamic bearing system to be provided at the openings of the bearing gap at first from the inside of the bearing with a reservoir region which widens outwards conically, which is adjoined by a gap seal provided with pump structures.

There is no bearing fluid in the pump seal in normal operating condition. In the case of greater shock action, bearing fluid can nevertheless pass from the fluid reservoir into the pumping seal, which subsequently immediately returns the bearing fluid back into the region of the capillary seal during operation of the bearing.

An advantageous embodiment of the invention provides an end arranged on the shaft pressure plate, on whose circumference the fluid reservoir is arranged. In particular, pressure plates may also be arranged at both ends of the shaft in the manner of a double axial bearing. Preferably, one side of the pressure plate with an opposite end face of the bearing bush forms a thrust bearing. The arrangement of a pressure plate in the sealing area results in a larger diameter in the region of the fluid reservoir and thus a larger volume of the fluid reservoir can be achieved or it is thereby possible with the same volume a shorter axial length of the bearing. Due to the outwardly adjoining pump seal the opening of the bearing is significantly lower than a capillary seal with a conical enlargement, whereby the fluid-air exchange and thus the evaporation rate of the fluid, such as the bearing oil, from the oil-air interface is significantly lower ,

While the width of the bearing gap is typically about 2-5 microns, the width of the seal gap, that is, the distance between the outer diameter of the pressure plate and the opposite surface of the bushing in the pumping seal region, is typically about 10 to 50 microns. The sealing gap initially increases in the area of the capillary seal, and narrows in the area of the pump seal.

In addition to the mentioned advantages in terms of the shock resistance of such a bearing results from the separation of the two main functions, on the one hand provide reservoir and on the other hand sealing the bearing for external shock, a greater design freedom to tune the seal to the specific requirements, eg. B. ratio of reservoir area to gap seal length, gap dimension, geometric arrangement of the two elements, as well as the possibility of an axial play of the bearing limiting element z. B. at the beginning of the gap seal between the two parts of the seal provided.

In addition, the better completion of the fluid reservoir achieves a smaller evaporation rate (hence possible to provide less reservoir for the same service life) and less dependence on manufacturing and filling tolerances compared to the conventional types of seals described. It is important for conical capillary seal compliance with the fill level and for gap seals the gap width, which may typically be not more than 10 microns.

Embodiments of the invention will be described below with reference to the drawings.

list of figures

• The 1 to 6 schematically show a first embodiment of a fluid bearing with inventive seal assembly. It schematically illustrates the distribution of the bearing fluid during a shock action on the bearing in chronological order.
• 7 schematically shows a second embodiment of a fluid bearing with inventive seal assembly.
• 8th schematically shows a third embodiment of a fluid bearing with inventive seal assembly.
• 9 schematically shows a fourth embodiment of a fluid bearing with inventive seal assembly.
• 10 schematically shows a fifth embodiment of a fluid bearing with inventive seal assembly.
• 11 schematically shows a sixth embodiment of a fluid bearing with inventive seal assembly.

Description of preferred embodiments of the invention

The structure and operation of the seal assembly for fluid bearing are first based on the 1 to 6 described.

The 1 to 6 show a section of a fluid bearing with inventive seal assembly.

The fluid bearing comprises a fixed bearing component, for example in the form of a shaft 10 with at least one end arranged pressure plate 14 , as well as a relative to this about a rotation axis 30 rotating bearing component, for example a. bearing bush 12 , Between the bearing components 10 . 14 and 12 is a bearing gap filled with a bearing fluid 16 formed, extending between opposing surfaces of the bearing components 10 . 14 respectively. 12 extends. One end of the pressure plate 14 forms with an opposite end face of the bearing bush 12 preferably a thrust bearing 32 , The fluid bearing also has at least one radial bearing 34 on, by appropriate surface structures on the shaft 10 or the bearing bush 12 is formed.

The open end of the storage gap 16 flows into a free space 18 which is substantially parallel to the axis of rotation 30 of the bearing and a conical capillary seal for the bearing gap 16 formed. The open space 18 is annular around the pressure plate 14 arranged and expands starting from the bearing gap 16 conical. The open space 18 serves as a capillary seal and at the same time as a reservoir for the bearing fluid, the free space 18 at least partially filled with bearing fluid whose surface due to the acting surface tension and adhesion forces a meniscus 20 formed. Alternatively or additionally, the free space through a recess in the pressure plate 14 be formed. To the through the free space 18 formed conical capillary seal closes a sealing gap 22 in the example shown also parallel to the axis of rotation 30 runs and is part of a pumping seal, which is characterized by pumping structures 24 is characterized on the surface of the printing plate 14 and / or the bearing bush 12 are located. During normal operation of the bearing, a fluid level is established 26 a, as he in 1 is shown.

The pump structures 24 are formed such that they rotate upon rotation of the shaft 10 and the associated printing plate 14 relative to the bearing bush 12 one in the camp interior, ie to the free space 18 directed pumping action, whereby, for example, by shock effect in the sealing gap 22 reached bearing fluid again from the sealing gap 22 back to the reservoir 18 is pumped.

It is now assumed the case that the fluid bearing according to 1 at rest one perpendicular to the conical reservoir area 18 is exposed to external impact vibration. First, the volume of fluid in the reservoir 18 by the acting lateral acceleration to one side of the annular reservoir 18 move. This is in 2 shown. In this case, a part of the supplied kinetic energy is already converted into internal energy of the bearing fluid, due to the greater surface energy due to the larger surface of the meniscus 20 in the right part of the reservoir 18 and less wetted metal, dissipation due to viscous friction in the fluid - which corresponds to the typical operation of a conical capillary seal.

Meets the meniscus 20 on the upper boundary of the conical space 18 , no additional kinetic energy is supplied, since further movement of the fluid is prevented. Here is an essential difference to the conical capillary seal, where this case only occurs when the external forces and the inertial forces of the fluid are in equilibrium with the capillary counter forces.

As soon as a part of the fluid touches the inner end of the gap sealing area, this part becomes in the sealing gap by the capillary forces 22 pulled - whereby even a fluid movement in the sealing gap 22 contrary to the external acceleration is possible. This condition is in 3 shown. Due to the narrow dimensions of the sealing gap 22 cause great losses due to viscous friction, causing the bearing fluid in the sealing gap 22 is slowed down.

When the fluid reaches the outer end of the gap sealing area, as shown in FIG 4 recognizes, builds because of the sudden expansion of the sealing gap 22 a strong back pressure on (usual functioning of a gap seal). Compared with a conventional, filled at rest by the capillary forces to the outer end with bearing fluid gap seal, the fluid there will be able to exert a much smaller pressure by the mechanisms described above and therefore first further laterally flow into the gap, as in 5 is shown; a possibility that does not exist in a conventional, completely filled with bearing fluid gap seal course. In the case of the usually very short-acting external vibrations, even before or during this process, the main part of the fluid reservoir is still present 18 fluid begin to return to the original rest position, whereby the pressure on the outer end of the gap seal is further reduced. After the end of the outer vibration, therefore, the main part of the fluid volume will again be in the conical reservoir area 18 and the area of the gap seal may be partially or completely filled, as in 6 is shown. If the bearing is now put into operation, the fluid content in the sealing gap 22 through the associated pump structures 24 Immediately return to the conical reservoir area 18 pumped, bringing the starting situation according to 1 is restored.

In the case of an external vibration acting along the conical reservoir region, first the same capillary mechanisms as in the conventional conical capillary seal or a gap seal at rest also occur.

A meniscal failure caused by inhomogeneities or tolerances in one location 20 or small fluid droplets dissolving as a result of excessive pressure compared to surface tension are trapped either directly through the upper confinement of the conical reservoir region (not present in conventional seal types) or in the gap seal region.

Obviously, the functions of the two cases described above in the rotating state of the storage system by the pump structures 24 further supported in the gap sealing area, which further increases the safety of the seal.

7 shows a schematic further embodiment of a fluid bearing with inventive seal assembly. A wave 110 is rotatable in a bearing bush 112 stored, where they filled with bearing fluid bearing gap 116 formed. The bearing gap 116 ends in a free space, which serves as a fluid reservoir 118 and capillary seal acts. The free space is proportionally filled with bearing fluid, wherein the fluid level 126 a meniscus 120 within the open space 118 formed. In continuation of the free space 118 closes a sealing gap 122 on, by opposing surfaces of the shaft 110 and the bearing bush 112 is formed. The sealing gap 122 is part of a pumping seal, which by arranged on the surface of the shaft or the bearing bush pump structures 124 is defined. In this embodiment, both the capillary seal, so the reservoir 118 , as well as the sealing gap 122 on the shaft 110 parallel to the axis of rotation 130 of the fluid bearing. Inside the warehouse is at least one radial bearing 134 arranged by surface structures on the shaft 110 and / or the bearing bush 112 is formed.

8th shows an embodiment of a fluid bearing with sealing arrangement, in which the shaft 210 relative to a bearing bush 212 is rotatably mounted. The upper end of the shaft carries an engine component 228 , This can be the hub when the shaft is rotating and the housing when the shaft is stationary. Between the wave 210 and the bearing bush 212 is a filled with bearing fluid bearing gap 216 in a clearance 218 opens, which serves as a fluid reservoir and capillary seal. The fluid level 226 in the open space is through a meniscus 220 characterized. Beyond the open space 218 namely perpendicular to the axis of rotation of the bearing is between opposing surfaces of the engine component 228 and the bearing bush 212 a sealing gap 222 formed, which is part of a pumping seal. The pump seal is characterized by pump structures 224 in the present example on the engine component 228 facing surfaces of the bearing bush 212 are arranged. Alternatively, the pump structures on the surface of the engine component 228 or be arranged on the opposite surfaces of both components.

9 shows a construction of a fluid bearing with a rotatable shaft 310 whose lower section forming a bearing gap 316 in a bushing 312 is stored. A radially extending surface of the hub 328 forms with an opposite surface of the bearing bush 312 a thrust bearing 332 , At the bottom of the shaft 310 can be a pressure or stopper plate 314 be provided or the shaft 310 can be made in one piece with a corresponding paragraph. At the upper end of the shaft, in the region of its larger diameter, is a rotor component 328 attached, the inside circumference a space 318 formed by the outer circumference of the bearing bush 312 is limited. The free space closes immediately at a radial portion of the bearing gap 316 and in this example runs approximately in the axial direction, ie in the direction parallel to the axis of rotation 330 of the camp. The flared end of the conical clearance is defined by a radially inwardly directed shoulder of the hub 328 limited, which together with the outside of the bearing bush 312 a sealing gap 322 which forms part of a pump seal. On one of the facing surfaces of the bearing bush 312 or the flange of the rotor component 328 are pump structures 324 arranged, which provide a pumping action of the pumping seal during rotation of the bearing. This in 9 shown bearing allows a very flat design, since the free space 318 not in extension of the bearing gap 316 but opposite to the axis of rotation 330 runs. The fluid bearing also has at least one radial bearing 334 on and it can also be between the bottom of the hub 328 and the top of the bearing bush 312 a thrust bearing 332 be arranged, which is formed by groove structures in the surface of at least one of the two opposing components.

10 shows an embodiment of a bearing that deviates from the camp in 9 a T-shaped shaft 410 Includes, in a bushing 412 is stored. On the outer circumference of the shaft is a rotor component 428 provided with its inner circumference together with an outer circumference of the bearing bush 412 a free space 418 training, which serves as a reservoir and capillary seal. Due to the special design of the T-shaped shaft 410 it is possible the hub 428 from the bottom of the bearing bush 412 to assemble, resulting in further Gestaftungsmöglichkeiten for the seal arrangement result. In this example, the clearance is at an angle of, for example, 45 ° to the axis of rotation 430 of the bearing, which has a positive effect on the shock resistance of the bearing. The rotor component 428 has a radially inwardly directed shoulder which, together with an opposite surface of the bearing bush 412 a sealing gap 422 forms part of a through pumping structures 424 characterized pump seal is. This paragraph at the lower end of the inner diameter of the rotor component 428 also acts as a stop, which serves as an axial stopper and limits an axial displacement of the movable bearing member.

In 11 an embodiment of a fluid bearing is shown, which is a modification of the embodiment according to the 1 to 6 represents. The fluid bearing comprises a fixed shaft 510 with a pressure plate arranged at one end 514 , as well as a relative to this about a rotation axis 530 rotating bushing 512 , Between the bearing bush 512 , the wave 510 and the printing plate 514 is a bearing gap filled with a bearing fluid 516 formed, extending between opposite surfaces of these bearing components 510 . 512 and 514 extends. The fluid bearing has a radial bearing 534 on, by appropriate surface structures on the shaft 510 or the bearing bush 512 is formed. Between opposite end faces of the pressure plate 514 and the bearing bush 512 is one at the bearing gap 516 adjoining open space 518 arranged, which is substantially perpendicular to the axis of rotation 530 of the bearing and a conical capillary seal for the bearing gap 516 formed. The open space 518 is annular below the pressure plate 514 arranged and expands starting from the bearing gap 516 radially on the outside conical. To form the conical shape of the free space 518 preferably has the bearing bush 512 a bevel on. Alternatively, this bevel also in the pressure plate 514 or be mounted in both components. The open space 518 serves as a capillary seal and at the same time as a reservoir for the bearing fluid and is at least partially filled with bearing fluid. The surface of the bearing fluid forms in the free space 518 due to the acting surface tension and the adhesion forces a meniscus 520 out. To the through the free space 518 formed conical capillary seal closes a sealing gap 522 in the example shown parallel to the axis of rotation 530 runs and is part of a pumping seal, which is characterized by pumping structures 524 is characterized on the peripheral surface of the printing plate 514 are located.
Because of the radially below the pressure plate 514 arranged free space 518 can the sealing gap 522 be formed longer or the height of the bearing can be reduced.

LIST OF REFERENCE NUMBERS

10

wave

12

bearing bush

14

printing plate

16

bearing gap

18

Fluid reservoir (free space)

20

meniscus

22

sealing gap

24

pumping structures

26

fluid level

30

axis of rotation

32

thrust

34

radial bearings

110

wave

112

bearing bush

116

bearing gap

118

fluid reservoir

120

meniscus

122

sealing gap

124

pumping structures

126

fluid level

130

axis of rotation

134

radial bearings

210

wave

212

bearing bush

216

bearing gap

218

Fluid reservoir (free space)

220

meniscus

222

sealing gap

224

pumping structures

226

fluid level

228

engine component

230

axis of rotation

234

radial bearings

310

wave

312

bearing bush

314

Pressure / stopper plate

316

bearing gap

318

Fluid reservoir (free space)

320

meniscus

322

sealing gap

324

pumping structures

328

hub

330

axis of rotation

332

thrust

334

radial bearings

410

wave

412

bearing bush

416

bearing gap

418

Fluid reservoir (free space)

420

meniscus

422

sealing gap

424

pumping structures

428

hub

430

axis of rotation

432

thrust

434

radial bearings

510

wave

512

bearing bush

516

bearing gap

518

Fluid reservoir (free space)

520

meniscus

522

sealing gap

524

pumping structures

530

axis of rotation

534

radial bearings

Claims (14)

A sealing arrangement for a fluid bearing with a bearing component (12) and a relative to this about a rotation axis (30) rotating bearing member (10), wherein the two bearing components are spaced by a bearing fluid filled with a bearing gap (16), wherein the bearing gap at least one having a sealed end sealed by a capillary seal and a pumping seal is provided, wherein the capillary seal between the bearing gap (16) and the pumping seal is arranged, characterized in that the one bearing member (10) comprises an annular pressure plate (14), and the capillary between an outer periphery of the pressure plate (14) and the other bearing member (12) is arranged. A seal assembly for a fluid bearing having a bearing member (312; 412) and a bearing member (310,410) rotating relative thereto about an axis of rotation (330; 430), the two bearing members separated from each other by a bearing gap (316; 416) filled with a bearing fluid the bearing gap having at least one open end sealed by means of a capillary seal and a pumping seal being provided, the capillary seal being arranged between the bearing gap (316; 416) and the pumping seal, characterized in that the movable bearing component (310, 410) an annular rotor member (328; 428), and the capillary seal is disposed between an inner circumference of the rotor member and the fixed bearing member (312; 412). Sealing arrangement for a fluid bearing with a bearing component (512) and a relative to this about a rotation axis (530) rotating bearing member (510), wherein the two bearing components by a bearing fluid filled with a bearing gap (516) are spaced from each other, wherein the bearing gap at least one having a sealed end sealed by a capillary seal and a pumping seal is provided, wherein the capillary seal between the bearing gap (516) and the pumping seal is arranged, characterized in that the one bearing member comprises an annular pressure plate (514), and the capillary seal between facing end faces the pressure plate (514) and the other bearing member (512) is arranged. Sealing arrangement according to one of Claims 1 to 3 , characterized in that the capillary seal is formed as a conical capillary seal. Sealing arrangement according to one of Claims 1 to 4 characterized in that the capillary seal forms a fluid reservoir (18; 318; 418; 518) for the bearing fluid which is at least partially filled with bearing fluid. Sealing arrangement according to one of Claims 1 to 5 characterized in that the pumping seal defines a sealing gap (22; 322; 422; 522) which is free of bearing fluid during normal operation of the fluid bearing. Sealing arrangement according to one of Claims 1 to 6 , characterized in that the capillary seal extends substantially parallel to the axis of rotation (30; 330; 430; 530) of the fluid bearing. Sealing arrangement according to one of Claims 1 to 6 , characterized in that the capillary seal extends substantially perpendicular to the axis of rotation (30; 330; 430; 530) of the fluid bearing. Sealing arrangement according to one of Claims 1 to 6 , characterized in that the capillary seal extends at an acute angle to the axis of rotation (30; 330; 430; 530) of the fluid bearing. Sealing arrangement according to one of Claims 1 to 9 , characterized in that the pumping seal extends substantially parallel to the axis of rotation (30; 330; 430; 530) of the fluid bearing. Sealing arrangement according to one of Claims 1 to 9 characterized in that the pumping seal extends substantially perpendicular to the axis of rotation (30; 330; 430; 530) of the fluid bearing. Sealing arrangement according to one of Claims 1 to 9 characterized in that the pumping seal extends at an acute angle to the axis of rotation (30; 330; 430; 530) of the fluid bearing. Sealing arrangement according to one of Claims 1 to 12 , characterized in that the capillary seal adjoins directly to a radial bearing region of the fluid bearing. Sealing arrangement according to one of Claims 1 to 12 , characterized in that the capillary seal adjoins directly to a thrust bearing region of the fluid bearing.

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