DE102019132914A1 - Fluid dynamic storage system - Google Patents

Abstract

The invention relates to a fluid dynamic bearing system with at least one conical bearing (14, 16), the conical bearing (14, 16) comprising a shaft (12) extending along an axis of rotation (62) on which a bearing component (18, 20) is fastened with a conical bearing surface, and a bearing bush (22) which has a conical bearing surface which lies opposite the conical bearing surface of the bearing component (18, 20) and is separated from this by a bearing gap (26, 28) filled with a bearing fluid, wherein the bearing gap (26, 28) has a first open end which is sealed by a first capillary sealing gap (32, 34) partially containing bearing fluid, and a second open end which is sealed by a second capillary sealing gap (36, 36) partially containing bearing fluid. 38) is sealed, the first and the second capillary sealing gap (32, 34; 36, 38) having widening conical sections and the bearing fluid in the conical Chen sections of the two sealing gaps fluid menisci (32a, 34a; 36a, 38a), the maximum gap widths of the conical sections of the first and second sealing gaps (32, 34; 36, 38) being approximately the same.

Description

The invention relates to a fluid dynamic bearing system according to the preamble of claim 1, which can preferably be used for the rotary bearing of a spindle motor. Such a fluid-dynamically mounted spindle motor can be used, for example, to drive a hard disk drive, laser scanner or fan.

Fluid dynamic bearing systems for the rotary bearing of spindle motors are known in various designs. Fluid dynamic bearing systems with one or more conical fluid dynamic bearings are used in particular for high loads, since conical fluid dynamic bearings have a high bearing rigidity and are therefore well suited for this purpose.

A conical fluid dynamic bearing generally comprises a shaft which extends along an axis of rotation and to which at least one bearing component with a conical bearing surface is attached. A bearing bush rotatably mounted relative to the bearing component has a conical bearing surface which lies opposite the conical bearing surface of the bearing component and is separated from it by a bearing gap filled with a bearing fluid. Two such conical fluid dynamic bearings are preferably combined with one another, each conical bearing having a conical bearing component arranged on the shaft, the conical bearing surfaces of which face one another.

The DE 10 2016 013 611 A1 discloses such a conical fluid dynamic bearing system for use in a hard disk drive. The two conical fluid dynamic bearings are completely separate from one another and each comprise a separate circuit for the bearing fluid. Each fluid dynamic bearing has a bearing gap which is arranged between the two bearing components rotating relative to one another and which has two open ends which are sealed by two capillary sealing gaps. The capillary sealing gaps are intended to reliably prevent bearing fluid from escaping from the fluid dynamic bearings due to vibrations or impacts acting on the bearing, both when the bearing is at a standstill and when the bearing is in operation. For use in mobile devices, ever more stringent requirements are placed on the vibration and shock resistance of the fluid dynamic bearing systems, so that the sealing arrangements also have to be continuously improved.

It is the object of the present invention to provide a conical fluid dynamic bearing system which has an improved resistance to so-called NOV (non-operating vibration) effects, ie. H. better resistance to external vibrations and shock when the bearing is at a standstill.

This object is achieved by a fluid dynamic bearing system with the features of claim 1.

Preferred embodiments of the invention and further advantageous features are specified in the subclaims.

The fluid dynamic bearing system has at least one conical bearing, the conical bearing comprising a shaft extending along an axis of rotation to which a bearing component with a conical bearing surface is attached, and a bearing bushing which has a conical bearing surface that corresponds to the conical bearing surface of the bearing component opposite and is separated from this by a bearing gap filled with a bearing fluid. The bearing gap has a first open end which is sealed by a first capillary sealing gap partially containing bearing fluid, and has a second open end which is sealed by a second capillary sealing gap partially containing bearing fluid, the first and second capillary sealing gaps being mutually exclusive have widening conical sections and the bearing fluid forms fluid menisci in the conical sections of the two sealing gaps.

According to the invention, the maximum gap widths of the conical sections of the first and second sealing gap are approximately the same size. The gap widths differ, for example, by a maximum of 10%.

The first and the second capillary sealing gap are connected to one another in a fluid-conducting manner via the bearing gap. When the bearing is at a standstill, the conical sections of the two sealing gaps have defined fill levels of the bearing fluid, with capillary forces acting in the sealing gaps forming concave fluid menisci at the interface between the bearing fluid and the ambient air. So that stable fluid menisci are formed in the sealing gaps, the invention provides that the gap widths of the conical sections of the two sealing gaps are essentially the same. This makes it possible for stable fluid menisci with the same width or the same cross-sectional area to form in the sealing gaps.

In a preferred embodiment of the invention, it is provided that the maximum gap width of the conical section of the second sealing gap is at least 1.15 times larger than the gap width of the conical section of the first sealing gap at the level of when the bearing is stationary forming fluid meniscus'. In other words, it is preferred if the gap width of the second sealing gap is at least 1.15 times greater than the width of the fluid meniscus in the first sealing gap that is established when the bearing is at a standstill. The conical section of the second sealing gap can thus be made shorter than the conical section of the first sealing gap.

In one embodiment of the invention, an annular gap filled with air or gas is arranged adjacent to the second sealing gap and is delimited by an outer circumferential surface of the shaft and an inner circumferential surface of the bearing bush. This annular gap is formed by an undercut in the shaft and an undercut in the bearing bore of the bearing bush.

The conical section of the second capillary sealing gap opens into the annular gap, wherein the gap width of the annular gap preferably corresponds to the maximum gap width of the conical section of the second sealing gap or can be larger.
In a preferred embodiment of the invention, the maximum gap width of the conical sections of the first and second sealing gap is between 0.4 mm and 0.6 mm, particularly preferably between 0.43 mm and 0.6 mm.

In order to avoid wetting of the annular gap with bearing fluid, it is preferably provided that the surfaces delimiting the annular gap are provided with a fluid-repellent coating. Preferably, however, the areas of the conical section of the second sealing gap directly adjoining the annular gap are not provided with the fluid-repellent coating.

For this purpose, it can be provided in a preferred embodiment of the invention that at least one groove is made on the surfaces of the shaft and the bearing bush in the area of the annular gap, which groove is arranged at a distance from the conical section of the second sealing gap. The groove serves as a barrier for the bearing fluid so that bearing fluid emerging from the second sealing gap cannot penetrate any further into the annular gap. Here, the surfaces of the groove in the annular gap can be at least partially provided with a fluid-repellent coating.

In a particularly preferred embodiment of the invention, the fluid dynamic bearing system comprises two conical fluid dynamic bearings which act against one another, adjoin one another, are essentially constructed in the same way and are separated from one another by the annular gap.

The fluid dynamic bearing system according to the invention can preferably be used for the rotary bearing of a spindle motor. Such a spindle motor is suitable for driving a hard disk drive, a laser scanner or a fan.

• 1 zeigt einen Schnitt durch einen Spindelmotor mit einem fluiddynamischen Lagersystem mit zwei konischen Lagern in einer ersten Ausgestaltung der Erfindung.
• 2 zeigt einen Schnitt durch einen Spindelmotor mit einem fluiddynamischen Lagersystem mit zwei konischen Lagern in einer zweiten Ausgestaltung der Erfindung.
• 3 zeigt eine vergrößerte Ansicht der Dichtungsbereiche des Lagersystems von 1.

A preferred embodiment of the invention is explained in more detail below with reference to the drawings. Further features and advantages of the invention emerge from the drawings and their description.

• 1 shows a section through a spindle motor with a fluid dynamic bearing system with two conical bearings in a first embodiment of the invention.
• 2 shows a section through a spindle motor with a fluid dynamic bearing system with two conical bearings in a second embodiment of the invention.
• 3rd FIG. 13 shows an enlarged view of the sealing areas of the bearing system of FIG 1 .

In 1 a section through a spindle motor with a fluid dynamic bearing system is shown. The bearing system includes two conical fluid dynamic bearings 14th , 16 .

The spindle motor includes a base plate 10 on which the engine and bearing components are built. In the base plate 10 a bore is arranged in which a shaft 12th is attached by means of a press connection and / or adhesive connection. On the wave 12th are two conical bearing components at an axial distance 18th , 20th arranged, each having a conical bearing surface. The conical bearing surfaces of the two bearing components 18th , 20th face each other and close with the axis of rotation 62 an angle of preferably 30 °. The base plate 10 forms with the wave 12th and the conical bearing components 18th , 20th the fixed bearing or motor component. In the illustrated embodiment, the shaft has a diameter of 3.5 mm.

The rotatable bearing or motor component comprises a bearing bush 22nd , which have a central bearing bore and two conical recesses to accommodate the conical bearing components 18th , 20th having. The bearing bush 22nd is by means of the two conical fluid dynamic bearings 14th , 16 rotatable around the shaft 12th and the conical bearing components 18th , 20th stored. The bearing bush 22nd is with a hub 24 connected, which carries the load of the spindle motor.

The two conical fluid dynamic bearings 14th , 16 are not connected to one another in a fluid-conducting manner, ie they do not share a common bearing gap filled with bearing fluid, but rather they are through an annular gap filled with air or a gas 30th axially and fluidically separated from each other. The annular gap 30th is formed by an undercut on the outer circumferential surface of the shaft 12th and an opposite undercut on the inner peripheral surface of the bearing bush 22nd . The annular gap 30th stands over one in the wave 12th provided longitudinal bore 12a and cross holes 12b , 12c in connection with the ambient atmosphere. The ambient atmosphere can contain air or a suitable gas, for example helium.

The first conical fluid dynamic bearing 14th is formed by a conical bearing surface of the first conical bearing component 18th and a corresponding and opposite conical bearing surface of the bearing bush 22nd . The two conical bearing surfaces are through a bearing gap 26th separated from each other, which is filled with a bearing fluid. At least one of the two conical bearing surfaces is provided with bearing groove structures, which when the bearing bush rotates 22nd around the wave 12th a pumping action on that in the bearing gap 26th Exercise located bearing fluid and thereby a fluid dynamic pressure in the bearing gap 26th produce.

The bearing gap 26th of the first conical bearing 14th is at its outer opening through a capillary sealing gap 32 sealed, which has a section which is conical in cross section and extends in the direction of the open end of the sealing gap 32 expands. The bearing gap is at its inner opening 26th through another capillary sealing gap 36 with a conical cross-section sealed into the annular gap 30th flows out. Along the inner sealing gap 36 is preferably a dynamic pump seal 40 arranged. To wet the surfaces of the annular gap 30th Using bearing fluid can avoid the surfaces of the annular gap 30th be provided with a fluid-repellent coating. The fluid-repellent coating can extend into the transition area between the annular gap 30th and the conical portion of the inner sealing gap 36 extend, but preferably the conical section is not provided with the fluid-repellent coating in order to prevent the bearing fluid from running out of the conical, inner sealing gap 36 reliably to be avoided even under shock conditions.

The bearing groove structures on the bearing surfaces of the first conical fluid dynamic bearing 14th are designed in such a way that they do this in the bearing gap 26th bearing fluid located predominantly in the direction of the interior of the bearing, ie in the direction of the inner sealing gap 36 promotes while the dynamic pump seal 40 is designed such that it is in the inner sealing gap 36 located bearing fluid in the direction of the conical bearing 14th promotes. One in the conical bearing component 18th intended recirculation channel 18a connects the transition between the bearing gap 26th and the inner sealing gap 36 directly with the transition between the bearing gap 26th and the outer sealing gap 32 . This allows the bearing fluid from the radially inner end of the bearing gap 26th directly back to the radially outer end of the bearing gap 26th flow, and there is a closed fluid circuit in the camp.

The external opening of the sealing gap 32 that the bearing gap 26th of the first conical bearing 14th seals, is from a cap 44 covered. The cover cap 44 is on one edge of the bearing bush 22nd attached. Between the opening of the sealing gap 32 and the cover cap 44 an air-filled ring-shaped free space remains 46 that has a gap seal 48 between the inner edge of the cap 44 and the outer circumference of the shaft 12th is connected to the ambient atmosphere and kept at ambient pressure.

The second conical fluid dynamic bearing 16 is preferably identical to the first conical fluid dynamic bearing 14th built up. The second conical bearing 16 is formed by the second conical bearing component 20th with a conical bearing surface, which has a conical bearing surface of the bearing bush 22nd opposite and from this through a bearing gap filled with a bearing fluid 28 is separated. At least one of the two conical bearing surfaces has bearing groove structures which, when the bearing surfaces rotate relative to one another, create a fluid dynamic pressure in the bearing gap 28 produce.

The openings of the second bearing gap 28 are through an external sealing gap 34 sealed as well as an internal sealing gap 38 that is in the annular gap 30th flows out. Along the inner sealing gap 38 is preferably a dynamic pump seal 42 arranged. To wet the surfaces of the annular gap 30th Avoid using bearing fluid, the surfaces of the annular gap 30th be provided with a fluid-repellent coating. The fluid-repellent coating can extend into the transition area between the annular gap 30th and the conical portion of the inner sealing gap 38 extend, but preferably the conical section is not provided with the fluid-repellent coating in order to prevent the bearing fluid from running out of the conical, inner sealing gap 38 reliably to be avoided even under shock conditions.

When the storage system is at a standstill, the outer sealing gap appears in the conical sections 32 , 34 and the conical sections of the inner seal gaps 36 , 38 an equilibrium of the capillary forces, which then the axial position of the fluid menisci 32a , 34a and 36a , 38a certainly.

The bearing groove structures on the bearing surfaces of the second conical fluid dynamic bearing 16 are designed in such a way that they do this in the second bearing gap 28 bearing fluid located predominantly in the direction of the interior of the bearing, ie in the direction of the inner sealing gap 38 promote while the dynamic pump seal 42 is designed such that it is in the inner sealing gap 38 located bearing fluid in the direction of the conical bearing 16 promotes. One in the conical bearing component 20th intended recirculation channel 20a connects the transition between the bearing gap 28 and the inner sealing gap 38 directly with the transition between the bearing gap 28 and the outer sealing gap 34 . This allows the bearing fluid from the radially inner end of the bearing gap 28 directly back to the radially outer end of the bearing gap 28 flow, and there is a closed fluid circuit in the camp.

The external opening of the lower sealing gap 34 is through a cover cap 50 covered, with between the opening of the sealing gap 34 and the cover cap 50 an annular space 52 remains, which has an annular gap seal 54 between the wave 12th and the cover cap 50 with a free space 68 is connected to the ambient pressure in which there is. The free space 68 is connected to the engine compartment via an air gap and to the outside environment via another air gap.

To fretting the conical bearings 14th , 16 To avoid this, one storage area of each warehouse can be used 14th , 16 , preferably the bearing surfaces of the conical bearing components 18th , 20th , be crowned. The conical bearing surfaces of the bearing components are used for this purpose 18th , 20th provided with a radius.

The two conical fluid dynamic bearings 14th , 16 do not have to be exactly the same. They can be in the area of their bearing surfaces and / or in the angle of the bearing surfaces in relation to the axis of rotation 62 distinguish. Furthermore, the two camps 14th , 16 be filled with storage fluids of different viscosity.

In the engine compartment is a stator assembly 56 arranged on the base plate 10 is attached. The stator assembly 56 opposite is a rotor magnet 58 on an inner peripheral surface of the hub 22nd arranged. As the hub 22nd is preferably made of aluminum, is on the inner circumferential surface of the hub 22nd a magnetic return 60 provided on which the rotor magnet 58 is attached. The electrical connection of the stator assembly 56 takes place on a circuit board 64 that are at the bottom of the base plate 10 is arranged and with which the winding wires 66 the stator windings are electrically connected.

3rd FIG. 3 is an enlarged view of FIG 1 and from the area of the two sealing gaps 32 , 36 of the first conical bearing 14th .

According to the invention is the largest gap width Sat the conical section of the outer sealing gap 32 about the same size as the largest gap width Si of the conical section of the inner sealing gap 36 . The maximum gap widths Sat , Si are, for example, between 0.4 and 0.6 mm. This also applies accordingly to the sealing gap 34 and 38 of the second conical bearing 16 .

It is particularly preferred if the maximum gap width Si of the conical section of the second sealing gap is at least 1.15 times larger than the gap width Sm the conical section of the outer sealing gap 32 at the level of the fluid meniscus 32a, which is located in the sealing gap when the bearing system is at a standstill 32 adjusts. The gap width also applies to the sealing gap 34 , 38 of the second conical bearing 16 .

The seal gap 32 limiting surfaces of the bearing bush 22nd and the conical bearing component 18th do not run parallel to the axis of rotation 62 but are at an angle of a few degrees radially inward in the direction of the axis of rotation 62 inclined. The outer peripheral surface of the conical bearing component 18th is inclined more radially inward than the inner circumferential surface of the bearing bush 22nd . This is the sealing gap 32 overall slightly inclined radially inward and widens conically in the direction of its open end, the angle of the conical widening being a few degrees.

The inner sealing gap 36 also widens conically, as the surfaces of the bearing bush that delimit the sealing gap 22nd and the wave 12th are preferably beveled at an angle of about 45 °. The opening angle of the conical widening of the inner sealing gap is thus 36 preferably about 90 °.

The sealing gap 34 and 38 of the second conical bearing 16 are preferably identical in their geometry to the sealing gaps 32 , 36 of the first conical bearing formed.

2 shows an opposite 1 slightly modified embodiment of a spindle motor with a fluid dynamic bearing system. The description of 1 applies to 2 . Identical components are denoted by the same reference symbols.

In contrast to 1 are in the area of the annular gap 30th on the surfaces of the shaft 12th and the bearing bush 22nd four grooves 70 , 72 intended. The grooves 70 are at a short distance from the End of the conical section of the second sealing gap 36 of the upper conical bearing 14th arranged while the other grooves 72 at a small distance from the end of the conical section of the second sealing gap 38 of the lower conical bearing 16 are arranged. The grooves 70 , 72 serve as a barrier for the bearing fluid, so that from the two inner sealing gaps 36 , 38 For example, bearing fluid escaping from the bearing as a result of a shock does not continue into the annular gap 30th can advance. Preferably the surfaces of the grooves are 70 , 72 provided with a fluid-repellent coating.

List of reference symbols

10

Base plate

12th

wave

12a

Longitudinal bore

12b

Cross hole

12c

Cross hole

14th

conical fluid dynamic bearing

16

conical fluid dynamic bearing

18th

conical bearing component

18a

Recirculation channel

20th

conical bearing component

20a

Recirculation channel

22nd

Bearing bush

24

hub

26th

Bearing gap

28

Bearing gap

30th

Annular gap

32

Sealing gap

32a

Fluid meniscus

34

Sealing gap

34a

Fluid meniscus

36

Sealing gap

36a

Fluid meniscus

38

Sealing gap

38a

Fluid meniscus

40

dynamic pump seal

42

dynamic pump seal

44

Cover cap

46

free space

48

Gap seal

50

Cover cap

52

free space

54

Gap seal

56

Stator assembly

58

Rotor magnet

60

magnetic return

62

Axis of rotation

64

Circuit board

66

Winding wire

68

free space

70

groove

72

groove

Sat

largest width of the sealing gap 32

Si

largest width of the sealing gap 36

Sm

Gap width of the sealing gap at the level of the fluid meniscus 32a

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 102016013611 A1 [0004]

Claims (15)

Fluid dynamic bearing system with at least one conical bearing (14, 16), the conical bearing (14, 16) comprising a shaft (12) extending along an axis of rotation (62) on which a bearing component (18, 20) with a conical bearing surface is attached, and a bearing bush (22) which has a conical bearing surface which lies opposite the conical bearing surface of the bearing component (18, 20) and is separated from it by a bearing gap (26, 28) filled with a bearing fluid, the bearing gap ( 26, 28) has a first open end which is sealed by a first capillary sealing gap (32, 34) partially containing bearing fluid, and has a second open end which is sealed by a second capillary sealing gap (36, 38) partially containing bearing fluid wherein the first and second capillary sealing gaps (32, 34; 36, 38) have flared conical sections and the bearing fluid in the conical sections of the two Sealing gap fluid menisci (32a, 34a; 36a, 38a), characterized in that the maximum gap width of the conical section of the second sealing gap (36, 38) is at least 1.15 times greater than the gap width of the conical section of the first sealing gap (32, 34) at the level of the fluid meniscus (32a, 34a), which occurs when the bearing system comes to a standstill in the first sealing gap (32, 34). Fluid dynamic storage system according to Claim 1 , characterized in that adjacent to the second sealing gap (36, 38) an annular gap (30) is arranged which is delimited by an outer circumferential surface of the shaft (12) and an inner circumferential surface of the bearing bush (22). Fluid dynamic storage system according to one of the Claims 1 or 2 , characterized in that the annular gap (30) is formed by an undercut in the shaft (12) and a radially opposite undercut in the bearing bore of the bearing bush (22). Fluid dynamic storage system according to one of the Claims 1 to 3rd , characterized in that the conical section of the second capillary sealing gap (36, 38) opens into the annular gap (30). Fluid dynamic storage system according to one of the Claims 1 to 4th , characterized in that the gap width of the annular gap (30) is at least as large as the maximum gap width of the conical section of the second sealing gap (36, 38). Fluid dynamic storage system according to one of the Claims 1 to 5 , characterized in that the surfaces of the shaft (12) and the bearing bush (22) are provided with a fluid-repellent coating in the area of the annular gap (30). Fluid dynamic storage system according to one of the Claims 1 to 6th , characterized in that the surfaces of the conical section of the second sealing gap (36, 38) adjoining the annular gap (30) are not provided with a fluid-repellent coating. Fluid dynamic storage system according to one of the Claims 1 to 7th , characterized in that the maximum gap widths of the conical sections of the first and second sealing gaps (32, 34; 36, 38) are between 0.4 and 0.6 mm. Fluid dynamic storage system according to one of the Claims 1 to 8th , characterized in that in the area of the annular gap (30) on the surfaces of the shaft (12) and the bearing bush (22) at least one groove (70, 72) is provided which is at a distance from the open end of the conical section of the second sealing gap (36, 38) is arranged. Fluid dynamic storage system according to one of the Claims 1 to 9 , characterized in that the surface of the groove (70, 72) in the annular gap is at least partially provided with a fluid-repellent coating. Fluid dynamic storage system according to one of the Claims 1 to 10 , characterized in that it has two counteracting conical fluid dynamic bearings (14, 16) which adjoin one another, are constructed identically and are separated from one another by the annular gap (30). Spindle motor with a fluid dynamic bearing system according to one of the Claims 1 to 11 . Hard disk drive with a spindle motor according to Claim 12 , Laser scanner with a spindle motor according to Claim 12 . Fan with a spindle motor according to Claim 12 .

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