DE102014007155A1 - Fluid dynamic bearing system for a spindle motor - Google Patents

Abstract

The invention relates to a fluid-dynamic bearing system, in particular for the rotary bearing of a spindle motor, with a first stationary bearing component, which has at least one shaft (12) arranged in a bearing bore, a stationary bearing component (16) receiving the shaft and an annular bearing component (18) arranged on the shaft ) and a second rotatable bearing component, which comprises at least one rotor component (14) with a bearing bush (14a), the two bearing components being separated from one another by a bearing gap (20) filled with a bearing fluid and by means of two axially spaced apart fluid dynamic radial bearings (22a) , 22b) and at least one fluid dynamic axial bearing (26) are rotatably mounted relative to each other, the bearing gap (20) having two open ends which are sealed by sealing gaps (32, 34), and the bearing bushing (14a) is a substantially radially extending annular Surface (48) forms with a ge opposite surface of the annular bearing component (18) forms a radially extending annular gap (47) which connects the bearing gap (20) with a first sealing gap (32). According to the invention, a circumferential groove (46) is provided in a radially outer section of the annular gap (47) in the annular surface (48) of the bearing bush (14a) or in the opposite surface of the annular bearing component (18).

Description

Field of the invention

The invention relates to a fluid dynamic bearing system for a spindle motor for supporting a rotatable engine component relative to a fixed engine component. Such spindle motors are used, for example, for driving storage disks in hard disk drives.

State of the art

From the prior art spindle motors with fluid dynamic bearing system going back to the applicant are known in which a fluid dynamic bearing system is used for mounting a rotor component, which consists of a combination of at least one fluid dynamic radial bearing and at least one fluid dynamic thrust bearing. A fluid dynamic bearing system usually consists of a fixed bearing component and a movable bearing component, which are separated by a filled with a bearing fluid bearing gap and rotatably supported about a common axis of rotation relative to each other. In a known manner bearing surfaces provided with bearing groove structures are present, which exert a pumping action on the bearing fluid in the bearing gap during rotation of the bearing. In fluid dynamic bearings, the bearing groove structures in the form of depressions or elevations are usually applied to one or both opposing bearing surfaces. Upon rotation of the bearing components relative to one another, the bearing groove structures generate a hydrodynamic pressure in the bearing gap. As a result of this hydrodynamic pressure, the two bearing components rotating relative to one another are separated and stored without contact by corresponding bearing forces.

A spindle motor with fluid dynamic bearing system is in the DE 10 2008 031 618 A1 disclosed. This bearing system comprises as a fixed bearing component a shaft which is held in a bore of a fixed bearing component. A movable bushing, which is part of a rotor component, rotates about the fixed shaft. The bearing system comprises two spaced fluid dynamic radial bearings and a magnetically biased fluid dynamic thrust bearing. Due to the fixed shaft design, the bearing gap comprises two open ends, each of which is sealed by a sealing gap. These sealing gaps are formed, for example, as static capillary seals or dynamic pump seals or a combination of these two types of seals.

At one end of the shaft, an annular bearing member is arranged, which is designed as a stopper member. In the region of the stopper component is a first sealing gap along which preferably an additional dynamic pumping seal is arranged. The sealing gap is connected to the bearing gap via a radially extending annular gap, which is arranged between a lower end face of the stopper component and an upper end face of the rotor component.

The axial height of the radially extending annular gap is relatively small, so that it may occur in an axial shock on the bearing that the axial height of the radially extending annular gap changes abruptly. For example, if the axial height of the radially extending annular gap increases abruptly, then the bearing fluid can not flow rapidly enough into the increased volume and a vacuum may form that promotes leakage of air bubbles from the bearing fluid.

The resulting air bubbles collect preferably in the region of this radially extending gap and can not easily escape via the sealing gap from the camp due to the very narrow sealing gap or the counteracting pumping flow of the dynamic pumping seal. If the accumulation of air becomes too great, it may affect the safe operation of the bearing.

It has also been observed that with prolonged high vibrations acting on the bearing at a standstill, it may happen that these vibrations cause a pumping action on the bearing fluid in the bearing gap, thus allowing small amounts of bearing fluid to escape from the bearing via the seal gap which are therefore no longer available for lubrication and beyond can cause contamination of the storage disks with bearing fluid. This can reduce the life of the storage or hard disk drive.

Another variant of the construction of the upper portion of the shaft ie the stopper element is in the DE 10 2011 025 369 A1 disclosed. In this spindle motor, the distance of the radial bearings (radial bearing span) is increased to achieve a higher rigidity of the bearing, while at the same time the upper sealing area is designed so that the bearing is more resistant to axial shock. The stopper element is formed for this purpose as part of the shaft and has a perpendicular to the axis of rotation extending, flat annular portion and a subsequent thereto cylindrical portion which extends in the axial direction and in one corresponding annular groove of the rotor member is arranged.

The font US 2010/0296190 A1 shows a bearing open on both sides with a standing shaft and two thrust bearings, which are arranged on two opposite end faces of the bearing bush.

Disclosure of the invention

The object of the invention is to provide a fluid dynamic bearing system for a spindle motor, in which an improved discharge of accumulating in the bearing air bubbles is provided, and leakage of bearing fluid is avoided from the sealing area, so that the reliability of the storage system is increased overall.

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 indicated in the dependent claims.

The fluid dynamic bearing system comprises a first fixed bearing component comprising a shaft disposed in a bearing bore, a fixed bearing member receiving the shaft, and an annular bearing member disposed on the shaft. A second rotatable bearing component comprises at least one rotor component with a bearing bush, wherein the two bearing components are separated by a bearing gap filled with a bearing fluid and rotatably supported relative to each other by means of two axially spaced fluid dynamic radial bearings and at least one fluid dynamic thrust bearing. The bearing gap has two open ends, which are sealed by sealing gaps. The bushing includes a radially extending annular surface which forms with a facing surface of the annular bearing member a radially extending annular gap connecting the bearing gap with a first sealing gap.

According to the invention, a circumferential groove is provided in the region of a radially outer portion of the annular gap either in the annular surface of the bearing bush or in the opposite surface of the annular bearing component. The groove is preferably arranged in the annular surface of the bearing bush and can in principle have any cross-section.

Because of this groove is located in the outer region of the radially extending gap more bearing fluid than in the inner region, so that in case of shock, the bearing fluid can flow into the inner region of the radially extending gap and there is no negative pressure, which promotes outgassing of air bubbles. The deeper the circumferential groove, the more effective this effect.

Even with strong vibrations acting on the bearing system, leakage of bearing fluid from the sealing area is effectively prevented by this inventive groove, since the bearing fluid is collected and retained in this groove and thus remains in the storage system. Again, the effectiveness of the effect increases the deeper the groove is. This retaining effect of the groove can be further enhanced by ensuring that the opening of a recirculation channel terminating in the annular gap preferably opens at least partially directly into the groove or the opening of the recirculation channel via a connecting channel which is located in the radial surface of the bearing bush or Within the surface of the annular bearing member has a depth of 10 to 400 microns, is connected to the circumferential groove. As a result, the bearing fluid in the groove can, if required, flow back into other areas of the bearing via the recirculation channel.

Preferably, the circumferential groove in the substantially radially extending surface of the bearing bush or the surface of the annular bearing member (stopper member) in the axial direction has a depth of 10 to 400 micrometers and in the radial direction has a width of at least 100 micrometers. The substantially radially extending surface of the bearing bush includes a radially extending abutment surface, which is characterized in that only forms a narrow radial gap between this abutment surface and the annular bearing member. The smaller the extent of the stop surface in the radial direction, the less friction occurs during rotation of the bearing, resulting in lower power consumption. Therefore, the extent of this stop surface in the radial direction is preferably less than two-thirds of the extent in the radial direction of the largely radial surface of the bearing bush.

In a preferred embodiment, the depth of the circumferential groove is at least six times as large as the axial height of the radially extending gap between the abutment surface and the annular bearing component. In a further preferred embodiment, the depth of the circumferential groove is at least ten times as large as the axial height of the radially extending gap between the stop surface and the annular bearing component.

The rotatable and the fixed bearing component have in the axial direction a margin (axial play) of 35 microns to each other, that is, they can move 35 μm in the axial direction relative to each other. During operation of the bearing, the rotatable bearing component adjusts to a certain axial height, so that the radially extending gap between stop surface and annular bearing component during operation of the bearing has an axial height between 15 microns and 25 microns.

The recirculation passage is preferably inclined at an angle between 3 degrees and 20 degrees relative to the rotation axis of the bearing. Here, a first upper opening at a smaller distance from the axis of rotation, as a second lower opening, which opens in the region of a radially extending gap between the thrust bearing and a second sealing gap. The upper opening of the recirculation channel opens preferably at least partially within the stop surface. The recirculation channel may for example have a diameter between 0.4 mm and 0.7 mm. It preferably has a diameter of 0.4 mm or 0.5 mm

Preferably, the diameter of the recirculation channel is at least 40% of the radial extent of the radially extending surface of the bearing component.

The accumulation of air bubbles in the camp or their discharge into the environment can be improved by further measures according to the invention. The first sealing gap is preferably formed by adjacent surfaces of the annular bearing member and the bearing bush, wherein on the first sealing gap defining surface of the annular bearing member or the bearing bush is provided at least one relief groove, preferably in parallel or at an angle greater than zero degrees with respect runs on the axis of rotation.

This relief groove essentially acts as a short circuit along the sealing gap, through which air bubbles accumulated in the region of the radially extending gap can escape into the environment along the sealing gap. In the storage system there is usually a greater pressure than in the environment (atmospheric pressure). The air bubbles are known to move in the direction of lower pressure and are thus discharged out of the storage system along the relief groove.

The relief groove in the area of the sealing gap has a sufficient depth, width or length, so that the air bubbles can easily escape through the relief groove into the open.

In a known manner, a dynamic pumping seal is additionally arranged along the first sealing gap with Pumprillenstrukturen which produce a pumping action on the bearing fluid in the bearing gap in the direction of the bearing interior, ie in the direction of the radially extending gap.

In an advantageous embodiment, the relief groove for discharging the air bubbles along the sealing gap may be formed as part of the pump groove structures of the pumping seal. In this case, the relief groove preferably has a greater length than the remaining pump groove structures and may additionally have a greater depth and / or a greater width, so that the two volumes adjacent to the first sealing gap are connected via the relief groove and thereby a good discharge of the accumulated air from the bearing - contrary to the pumping direction of the bearing fluid acting on the pump seal - is given. The depth of the relief groove in the region of the dynamic pump seal is preferably at least 12 micrometers and is usually between 0.05 mm and 0.2 mm. The width can be between 0.1 mm and 0.5 mm and is usually between 0.1 mm and 0.2 mm. The pumping groove structures of the dynamic pumping seal typically have a depth of 12 microns and a width of between 0.1 mm and 0.2 mm.

In a preferred embodiment may be provided on the abutment surface between the annular bearing member and the bearing bush a plurality of radially extending or obliquely to the radius grooves. By these radially extending or obliquely to the radius grooves, an improvement of the distribution of the bearing fluid is achieved in the annular gap. These grooves also favor the flow of the bearing fluid through the radially extending gap, especially in the event of a shock. The grooves may be formed either radially extending, so that they exert no special pumping action on the bearing fluid in the radially extending annular gap during rotation of the bearing system. However, the grooves can also be arranged obliquely to the radius and, during a rotation of the bearing system, act as pump groove structures, which preferably pump the bearing fluid located in the radially extending gap inwards in the direction of the bearing gap. Preferably, these grooves may have a greater depth and / or a greater length and / or a greater width than the pump groove structures.

If the grooves are formed obliquely to the radial direction and thereby generate a pumping action on the bearing fluid during rotation of the bearing system, they can also act as a second thrust bearing, which generates a counterforce to the first, bottom thrust bearing. Because larger air bubbles always move in the direction of lower pressure, the air bubbles move against the pumping direction of the obliquely to the radial direction formed grooves and can travel through the grooves in the region of the circumferential groove and then along the first sealing gap through the relief groove, for example, as part of the dynamic pumping seal is designed to escape to the outside.

The grooves on the substantially radially extending surface along the radially extending gap preferably have a depth of 10 microns to 20 microns and a width of 0.1 mm to 0.5 mm.

The fluid dynamic bearing system is suitable for the rotary mounting of a spindle motor. Such a spindle motor may preferably be used in a hard disk drive and rotationally drive at least one disk, the hard disk drive having a write-read device for writing and reading data to and from the disk.

Preferred embodiments of the invention will now be explained in more detail with reference to the following drawing figures. This will become apparent from the drawings and the following description of further features and advantages of the invention.

Brief description of the drawings

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

1a shows a section through the spindle motor of 1 with a modified embodiment of the detail X of 1 ,

2 shows an enlarged view of the rotor component in the region of the upper sealing gap according to a first embodiment of the invention.

3 shows an enlarged view of the rotor component in the region of the upper sealing gap according to a second embodiment of the invention.

4 shows a section through a further embodiment of a storage system according to the invention.

5 shows an enlarged detail of the detail Y of 4 ,

6 shows a modified embodiment of the detail Y of 4 ,

7 shows a modified embodiment of the detail Y of 4 ,

8th shows a modified embodiment of the detail Y of 4 ,

9 shows a modified embodiment of the detail Y of 4 ,

10 shows a perspective view of the rotor component.

11 shows a perspective view of the rotor component according to 2 ,

12 shows a section through a further embodiment of a storage system according to the invention.

13 shows an enlarged detail of the detail Z of 11 ,

14 shows a modified embodiment of a storage system according to the invention.

15 shows a modified embodiment of the detail Y of 4 ,

Description of preferred embodiments of the invention

The 1 shows a spindle motor with a fluid dynamic bearing according to the invention. Such a spindle motor can be used to drive disks of a hard disk drive.

The spindle motor comprises a base plate 10 having a substantially central cylindrical opening in which a fixed bearing member 16 is included. The fixed bearing component 16 is approximately cup-shaped in cross-section and comprises a central opening, in which a shaft 12 is attached. At the free end of the fixed shaft 12 is an annular bearing component 18 arranged, preferably in one piece with the shaft 12 is trained. The named components 10 . 12 . 16 and 18 form the fixed bearing component of the spindle motor. The wave 12 has at its upper end a threaded bore (not shown) for attachment to a housing cover of the spindle motor or the hard disk drive.

The fluid-dynamic bearing system comprises a rotor component 14 with a molded bushing 14a in one by the shaft 12 and the two bearing components 16 . 18 formed intermediate space is rotatably arranged relative to these components. The upper annular bearing component 18 is in one annular recess of the bearing bush 14a arranged. Adjacent surfaces of the shaft 12 , the bearing bush 14a and the two bearing components 16 . 18 are by a bearing gap open on both sides 20 separated from each other, which is filled with a bearing fluid, such as a bearing oil.

The electromagnetic drive system of the spindle motor is formed in a known manner by a on the base plate 10 arranged stator arrangement 42 and an annular permanent magnet concentrically surrounding the stator assembly at a distance 44 at an inner circumferential surface of the rotor component 14 is arranged.

The on the rotor component 14 arranged bearing bush 14a has a cylindrical bore, on whose inner circumference two cylindrical radial bearing surfaces are formed, which by an intermediate separator gap 24 are separated. The bearing surfaces enclose the standing shaft 12 at a distance of a few microns to form an axially extending portion of the bearing gap 20 and form with each opposite bearing surfaces of the shaft 12 two fluid dynamic radial bearings 22a . 22b , which are provided with sinusoidal or parabolic Lagerrillenstrukturen.

To the lower radial bearing 22b closes a radially extending portion of the bearing gap 20 on, by radially extending bearing surfaces of the bearing bush 14a and corresponding opposite bearing surfaces of the fixed bearing component 16 is formed. These bearing surfaces are considered to the axis of rotation 38 formed perpendicular circular rings and form a fluid dynamic thrust bearing 26 , The fluid dynamic thrust bearing 26 is characterized in a known manner by, for example, spiral bearing groove structures, either on the front side of the bearing bush 14a , the fixed bearing component 16 or both parts can be attached. Advantageously, all are for the radial bearings 22a . 22b and the thrust bearing 26 necessary Lagerrillenstrukturen on bearing surfaces of the bearing bush 14a arranged what the production of the bearing, in particular the shaft 12 and the fixed bearing component 16 simplified.

Preferably, the bearing grooves of the thrust bearing 26 without interruption within the bearing bush 14a in the radial direction of the bore diameter for receiving the shaft 12 to the outer circumference of the bearing bush 14a , In a radially inner region of the thrust bearing 26 is the radial portion of the bearing gap 20 about 10 microns, while in a radially outer region of the bearing gap 20 in a gap about 20 microns to 100 microns wide 27 expands into which a lower second opening of a recirculation channel 28 empties.

To the radial gap 27 closes a conically opening, almost axially extending, proportionally filled with bearing fluid sealing gap 34 on, by opposing surfaces of the bearing bush 14a and the fixed bearing component 16 is formed and the open end of the bearing gap seals. In addition to the function as a capillary seal, the sealing gap is used 34 as a fluid reservoir and provides the required for the life of the storage system fluid amount. Furthermore, filling tolerances and a possible thermal expansion of the bearing fluid can be compensated. The two of the conical section of the sealing gap 34 forming surfaces on the bearing bush 14a and the fixed bearing component 16 can each relative to the axis of rotation 38 to be inclined inwards. As a result, the bearing fluid in a rotation of the bearing due to the centrifugal force inward in the direction of the bearing gap 20 pressed.

On the other side of the storage system is the bearing bush 14a following the upper radial bearing 22a designed so that it has a substantially radially extending surface 48 ( 2 ) formed with a corresponding opposite surface of the second annular bearing member 18 a radially extending gap 47 forms. To the radial gap 47 closes an axially extending sealing gap 32 which terminates the fluid bearing system at this end. The sealing gap 32 is made by opposing surfaces of the bearing bush 14a and the annular bearing component 18 limited and widens in the direction of its outer end with preferably conical cross-section. Along the sealing gap 32 is preferably a dynamic pumping seal 36 arranged the groove structures 36a comprises, which upon rotation of the bearing a pumping action on the sealing gap in the gap 32 bearing fluid in the direction of the bearing gap 20 exercise. The sealing gap 32 is preferably of an annular cap 30 covered, for example, at one stage of the bearing bush 14a held and there glued, for example. The inner edge of the cap 30 can be together with the outer circumference of the shaft 12 form a gap seal. This increases the safety against leakage of bearing fluid from the seal gap 32 ,

In the bearing bush 14a is a recirculation channel 28 arranged, starting from the surface 48 the bearing bush 14a in the region of the gap axially downwards and obliquely radially outwards along the bearing bush 14a runs and in the radially outer region of the thrust bearing 26 in the gap 27 empties. The recirculation channel 28 is at an angle between 3 degrees and 20 degrees relative to the axis of rotation 38 inclined, wherein the first upper opening of the recirculation channel 28 in the region of the radially extending gap 47 a smaller distance to the axis of rotation 38 as the second lower opening of the recirculation passage 28 , which in the region of the radially extending gap 27 empties. The diameter of the recirculation channel 28 is usually between 0.4 mm and 0.7 mm, preferably 0.4 mm or 0.5 mm. The diameter of the recirculation channel 28 is preferably at least 40% of the radial extent of the surface 48 , Since the spindle motor only a single fluid dynamic thrust bearing 26 that points to the rotor component 14 a force in the direction of the second annular bearing component 18 generated, a corresponding counterforce or biasing force must be provided on the movable bearing part, which holds the bearing system axially in balance. For this purpose, the base plate 10 a ferromagnetic ring 40 on, the rotor magnet 44 axially opposite and is magnetically attracted by this. This magnetic attraction acts against the force of the thrust bearing 26 and keeps the bearing axially stable. Alternatively or in addition to this solution, the stator assembly 42 and the rotor magnet 44 axially offset from each other, in such a way that the magnetic center of the rotor magnet 44 axially further away from the base plate 10 is arranged as the center of the stator assembly 42 , Also, an axial force is built up by the magnet system of the motor, which is opposite to the thrust bearing 26 acts.

According to the invention is located in the radially outer region of the surface 48 the bearing bush 14a a relatively deep, preferably circumferential groove 46 , which is filled with bearing fluid, as well as the gap 47 and the sealing gap 32 , In this groove 46 also opens at least partially the recirculation channel 28 or is with this via a connection channel 49 connected.

The circumferential groove 46 serves as a compensating volume for the bearing fluid in the event of a shock, leaving it within the area 48 between the bearing bush 14a and the annular bearing component 18 bearing fluid over the groove 46 as well as the gap 47 in the recirculation channel 28 can drain away, rather than in the area of the sealing gap 32 to be displaced.

In the axial direction, the depth of the groove 46 preferably between 10 microns to 400 microns, while in the radial direction the width of the groove 46 preferably at least 100 microns. Particularly preferred is the depth of the circumferential groove 46 in the axial direction 200 microns.

In an alternative embodiment of the invention, the circumferential groove is not in the area 48 the bearing bush 14a but in the opposite surface of the annular bearing member 18 ( 1a ), preferably on the outer circumference of the annular bearing component, for example in the form of a chamfer or a comparatively large radius.

Between a chamfer or a radius in the transition area of the hole inside the bearing bush 14a for receiving the shaft 12 as well as the circumferential groove 46 There is a radially extending abutment surface 48a , The upper part of the recirculation channel 28 opens at least partially in the area of this stop surface 48a , The extent of the stop surface 48a in the radial direction is preferably less than two-thirds of the total radial extent of the surface 48 ,

Along the first sealing gap 32 is preferably a dynamic pumping seal 36 arranged the corresponding pump groove structures 36a has, with a rotation of the bearing system, a pumping action on the sealing gap in the 32 located bearing fluid in the direction of the radially extending gap 47 into the interior of the camp.

Due to the relatively small width of the first sealing gap 32 it is for air bubbles that are in the area of the radial gap 47 have accumulated, difficult, over the sealing gap 32 escape to the outside. Therefore, it is provided in a preferred embodiment of the invention that extends along the first sealing gap 32 at least one special groove 37 extends, either on the surface of the bearing bush 14a or on the surface of the annular bearing component 18 is arranged. This groove 37 can, as in the example in 1 is shown as part of the pump groove structures 36a be educated.

However, the groove possesses 37 preferably a greater length and may additionally have a greater width and / or greater depth than the remaining pump groove structures 36a have, so that the two at the sealing gap 32 adjacent volumes over the groove 37 connected and thus a good discharge of the accumulated air from the region of the radially extending gap 47 or the circumferential groove 46 given is.

It can also have several grooves 37 distributed over the circumference of the first sealing gap 32 be arranged.

The 1a shows a modified embodiment of the detail X of the 1 , Here is the circumferential groove 46 not like in 1 in the bearing bush 14a incorporated, but in the annular bearing component 18 in the form of a chamfer on the outer circumference of the annular bearing component 18 , The recirculation channel 28 flows at least partially into the circumferential groove 46 , That in the groove 46 located bearing fluid can therefore without major Resistance in the recirculation channel 28 flow in or out of the recirculation channel 28 into the groove 46 flow out.

2 shows a partial section through the rotor component of 1 Taking the pump groove structures 36a the pump seal 36 recognizes and also the specially trained groove 37 as part of the pump-well structures 36a is trained.

It also recognizes the circumferential groove 46 in the radially outer region of the surface 48 the bearing bush 14a , Preferably, the stop surface 48a additionally with groove structures 50 be provided, which are arranged, for example, obliquely to the radial direction.

These groove structures 50 are formed so that they upon pump rotation on the pump in the radially extending gap 47 located bearing fluid inward in the direction of the radial bearing gap 20 generate and thus a second upper thrust bearing 52 form. These grooves 50 are preferably formed deeper and may additionally be formed wider than the pump groove structures 36a and therefore allow the radially extending gap 47 contained air bubbles radially outward through the grooves 50 in the area of the circumferential groove 46 wander and then along the first sealing gap 32 through the groove 37 can escape to the outside.

Since larger air bubbles always move in the direction of lower pressure, these air bubbles move against the pumping direction of the pump groove structures 36a and also against the pumping direction of the grooves 50 on the stop surface 48a , Further, as smaller air bubbles move in the direction of flow of the bearing fluid, they become within the radially extending gap 47 radially outward into the circumferential groove 46 promoted.

3 shows a modified embodiment of the invention and an enlarged section through the bearing bush 14a ,

Unlike the 2 includes the radially extending abutment surface 48a now grooves 150 which extend in the radial direction to the outside. Due to the radial orientation, the grooves create 150 no defined pumping action on the in the gap 47 located bearing fluid, but improve the distribution of the bearing fluid in the radially extending gap 47 by turbulence of the bearing fluid. From the circumferential groove 46 Air bubbles can via a separately arranged, preferably in the axial direction groove 137 through the region of the first sealing gap 32 escape to the outside. The groove 137 is in addition to the groove structures 36a the dynamic pump seal 36 on the surface of the bearing bush 14a or the surface of the annular bearing component 18 intended.

The present invention may include several embodiments according to the above-described embodiments.

In all embodiments, the circumferential groove 46 at the largely radial surface 48 in the area of the gap 47 intended.

In addition to the groove 46 can have oblique grooves 50 or radially extending grooves 150 on the stop surface 48a be provided.

It can also only corresponding grooves 37 respectively. 137 in the region of the first sealing gap 32 in addition to the circumferential groove 46 be provided.

But it can also all structures, ie the circumferential groove 46 , the oblique grooves 50 or the radially extending grooves 150 and the grooves 37 respectively. 137 in the region of the first sealing gap 32 be provided to ensure optimum discharge of air bubbles in the warehouse over the first sealing gap 32 to allow outward and an improvement of the distribution of the bearing fluid in the radially extending gap 47 to reach.

4 shows a section through one opposite 1 modified embodiment of a spindle motor with fluid dynamic storage system. The same components or components with the same functions are denoted by the same reference numerals as in 1 designated. Overall, the spindle motor of 4 a much lower height than the spindle motor of 1 and is z. B. suitable for installation in flat, portable devices. Due to the low overall height of the fluid dynamic bearing system, the axial length of the first sealing gap 32 relatively small and also the length of along the first sealing gap 32 provided pump groove structures 36a the pump seal 36 is compared to 1 considerably reduced.

In contrast, the length of the radially extending annular gap 47 about the same size or even larger than the corresponding gap in 1 , In the radially extending gap 47 limiting area 48 the bearing bush 14a is in turn a circumferential groove 46 arranged.

As can be seen in the enlarged view of detail X of 5 detects, is the radial gap 47 formed such that its axial height increases significantly radially outward, so that the circumferential groove 46 forming in the radially outer portion of the gap 47 reached its greatest depth of, for example, 200 microns. The area 48 the bearing bush 14a is beveled radially outwards, so that the depth of the groove 46 enlarged to the outside. The recirculation channel 28 flows at least partially into the groove 46 , where the gap 47 already deeper. That in the groove 46 Accordingly, bearing fluid can thus easily and without much resistance in the recirculation channel 28 flow in or out of the recirculation channel 28 into the groove 46 flow out.

In 6 is one opposite 5 modified embodiment of the circumferential groove 46 shown. Here is the area 48 the bearing bush 14a compared to 5 inclined radially outward at a steeper angle. As a result, the radially extending gap widened 47 to a groove 46 with greater depth compared to 5 , The maximum depth of the groove 46 is in this embodiment 400 Micrometers. The groove 46 has an overall larger cross-section and a larger volume than the groove 46 from 5 , The recirculation channel 28 flows at least partially into a deeper area of the groove 46 ,

7 shows an embodiment which is substantially the embodiment of 6 equivalent. The area 48 the bearing bush 14a is about the same angle as in 6 inclined radially outwards, the surface 48 However, in the radially outer region is no longer inclined, but parallel to the opposite surface of the annular bearing member 18 runs. This has the groove 46 in the radially outer region a constant depth of, for example, 200 microns and has an overall smaller cross section and a smaller volume than the groove 46 from 6 , The recirculation channel 28 flows at least partially into a deeper area of the groove 46 ,

8th shows a further embodiment of a fluid dynamic bearing with a modified embodiment of a groove 46 , That at the top of the shaft 12 attached annular bearing component 18 has one opposite the shaft 12 enlarged outer diameter and thus serves as an axial end stop for the bearing bush 14a , Between the outer circumference of the annular bearing component 18 , as well as the opposite inner circumference of the bearing bush 14a is a sealing gap 32 with a pumping seal 36 arranged, with the pumping seal 36 by groove structures running obliquely to the axis of rotation 36a is formed, which pump the bearing fluid in the bearing interior during operation of the bearing. In the axial extension of the sealing gap 32 in the direction of the bearing interior there is a groove 46 within the area 48 , which has a recess opposite to the axial abutment surface of the annular bearing component 18 serving surface 48a the bearing bush 14a represents and is filled with bearing fluid. A recirculation channel 28 connects an area that is radially outside the lower thrust bearing 26 and radially within the lower capillary seal 34 is arranged, with the upper radial bearing gap 47 , The upper end of the recirculation channel 28 opens at least partially in the region of the radially extending abutment surface 48a , The upper mouth of the recirculation channel 28 does not run directly into the circumferential groove in this embodiment 46 but is through a radially extending connecting channel 49 , which has a depression in the area of the stop surface 48a represents, with the concentric circumferential groove 46 connected. The depth of the connection channel 49 can be in the range between 10 microns and 0.4 mm. The axial height of the connection channel 49 in the direction of rotation is preferably at least as large as the diameter of the recirculation channel 28 ,

9 shows a further embodiment example of the fluid dynamic bearing with a modified embodiment of the groove 46 , The depth of the groove 46 is here 10 microns and can, for example, by a machining method or alternatively by the method of electro-chemical machining (ECM) in the surface of the bearing bush 14a be incorporated. The removal of the groove 46 can in particular at the same time with the operation of deburring the upper mouth of the recirculation channel 28 respectively. Furthermore, if needed, the production of the connection channel 49 also be done with the same procedure in the same step.

15 shows a further embodiment of the fluid dynamic bearing with a modified embodiment of the circumferential groove 46 , The recirculation channel 28 opens completely within the radially extending abutment surface 48a , This is the recirculation channel 28 only over the radial gap 47 with the circumferential groove 46 connected and not, as in previously shown figures, via a connection channel 49 with greater axial height or in that the recirculation channel 28 at least partially in the circumferential groove 46 empties. The embodiment according to 15 has the advantage that the non-repeatable runout (NRRO) is very low.

10 shows a view of the bearing bush 14a , It can be seen in the middle of the bearing bore to which radially outward the surface 48 followed. In the radially outer region of the surface 48 is the circumferential groove 46 arranged. Between the recirculation channel 28 and the incorporated groove 46 a connection is preferably present, especially if the bearing bush 14a at standstill of the bearing on the stopper component 18 is applied. Therefore, it is provided between the groove 46 and at least a portion of the recirculation channel 28 a connection of at least 10 microns depth persists, even if the radial gap 47 between the area 48 the bearing bush 14a and the annular bearing component 18 (Stopper component) almost disappears. This connection between groove 46 and recirculation channel 28 can be generated in different ways. For example, the recirculation channel opens 28 not immediately in the groove in this embodiment 46 but is through an opening of the recirculation channel 28 surrounding recess or recess with the groove 46 connected.

11 shows a view of the 2 , It can be seen in the middle of the bearing bore for receiving a shaft 12 , to which radially outward the surface 48 connects, in which the stop surface 48a located. Clearly visible are the grooves 50 , which are oblique to the radial direction on the stop surface 48a are arranged and thereby an upper thrust bearing 52 represent. The pumping direction of the upper axial bearing acts radially inwards in the direction of the bearing bore.

12 shows a fluid dynamic storage system with respect to the 4 further reduced axial height. The bearing consists of a T-shaped standing shaft 12 , which has a larger outer diameter at the bottom, the outer circumference with a fixed bearing component 16 which in turn is mounted in a base plate (not shown in the drawing) of a hard disk drive. In this case, the radially extending bearing gap, which is formed by the T-shaped portion 12a the wave 12 and the bearing bush 14a , preferably smaller than the radially extending bearing gap 27 formed between the fixed bearing member 16 and the bearing bush 14a , In gap 27 opens a recirculation channel 28 , The radial gap 27 between the fixed bearing component 16 and the bearing bush 14a kinks in the axial direction and forms a sealing gap 34 made, which is arranged between the inner periphery of the fixed bearing component 16 as well as the outer circumference of the bearing bush 14a , This sealing gap 34 has the form of a conical capillary seal which opens to the outside of the bearing. In this case, at least the outer circumference of the bearing bush 14a in the area of the sealing gap 34 viewed in the axial direction upward in the direction of the axis of rotation 38 tilted by a small angle between 10 degrees and 2 degrees. The opposite, the sealing gap 34 radially outwardly bounding inner wall of the fixed bearing component 16 extends in the axial direction or is optionally at least in an area in which bearing fluid is, also viewed in the axial course upwards in the direction of the axis of rotation 38 tilted at an angle between zero degrees and 8 degrees. The angle of inclination of the outer circumference of the bearing bush 14a is always at least 2 degrees greater than the angle of inclination of the inner wall of the fixed bearing component in the area of the capillary seal 16 in the area of the capillary seal.

Between the top of the widened T-shaped section 12a the wave 12 and the opposite bottom of the bearing bush 14a there is a thrust bearing 26 , which is formed by spiral-shaped bearing grooves, preferably in the surface of the bearing bush 14a are formed and preferably from the edge of the center hole for receiving the shaft 12 to the outer diameter of the bearing bush 14a run.

At the axially upper end of the shaft 12 there is an annular bearing component 18 with one opposite the outer circumference of the shaft 12 widened outer diameter. The annular bearing component 18 has a radially extending portion 18a and a radially outer, approximately hollow cylindrical portion 18b on. The hollow cylindrical section 18b runs downwards in the axial direction. A rotatable rotor component 14 is in one piece with the bearing bush 14a connected and has on an inner peripheral surface of a rotor magnet 44 and at least one magnetic storage disc (not shown in the drawing) attached to the outer peripheral surface of the rotor member. Between the outer circumference of the hollow cylindrical section 18b the annular bearing component 18 and an opposite inner circumference of the bearing bush 14a there is a first sealing gap 32 which is designed as a conical capillary seal. Axial above the sealing gap 32 there is a cap 30 which prevents bearing fluid from leaking to the top of the bearing. Along the outside diameter of the shaft 12 are two radial bearings 22a . 22b in the region of the axially extending bearing gap 20 between the inner circumference of the bearing bush 14a and the outer diameter of the shaft 12 arranged. The radial bearings are formed by herringbone or sinusoidal bearing grooves. The upper, the annular bearing component 18 adjacent radial bearings 22a consists of an upper, down-pumping section, as well as a lower, up-pumping section and is formed symmetrically, which means that the upper and the lower section have the same axial length. In contrast, the lower radial bearing 22b formed asymmetrically by the lower, up-pumping portion is formed longer in the axial direction, as the upper, downwardly pumping portion. Between both radial bearings 22a . 22b There is an area that has no bearing grooves and has a radial bearing gap enlarged relative to the radial bearing gaps. This area is called Separatorspalt 24 designated.

At the axially upper end of the shaft 12 is an annular bearing component 18 arranged on one step of the shaft 12 rests, for example by means of a press fit with the shaft 12 is connected and extending in the radial direction portion 47 of the storage gap 20 with the opposite top of the bushing 14a forms. The the annular bearing component 18 opposite surface 48 the bearing bush 14a has in the radially outer region a recess for receiving the hollow cylindrical portion 18b the annular bearing component 18 on. The section extending radially in this area 47a of the storage gap 20 has a greater axial height than the radially extending gap 47 in the area of the stop surface 48a , The recirculation channel 28 connects an area of the storage gap 20 between the underside of the radial section 18a the annular bearing component 18 and the area 48 the top of the bearing bush 14a with the radially extending gap 27 that is radially outward of the lower thrust bearing 26 is arranged.

13 shows an enlarged section Z of the 12 in the region of the annular bearing component 18 at the top of the shaft 12 is attached. Between the annular bearing component 18 and the area 48 on the top of the bearing bush 14a there is a first radially extending section 47 of the storage gap 20 in which the recirculation channel 28 empties. In the course radially outward, the bearing gap kinks 20 initially directed in the axial direction downwards and then runs again, as a gap 47a , in the radial direction before it between the outer circumference of the annular bearing member 18 and an inner peripheral surface of the bearing bush 14a in the largely axially extending sealing gap 32 empties. This sealing gap 32 is designed as a conical capillary seal, which is limited by an axially extending wall of the bearing bush 14a and an inclined outer circumferential surface of the hollow cylindrical portion 18b the annular bearing component 18 , Between the mouth of the recirculation channel 28 and the cylindrical section 18b the annular bearing component 18 there is a circumferential groove 46 entering the recirculation channel 28 opens and a much greater axial depth compared to the portion of the radially inner gap 47 in the region of the radially extending abutment surface 48a having. The top of the annular bearing component 18 preferably has no edges or no small radii, so that the introduced during the filling process bearing fluid without residues (drops) on the sealing gap 32 in the storage gap 20 arrives.

14 shows one in the top of the bearing bush 14a modified fluid dynamic bearing. Again, the recirculation channel opens 28 within the radially extending gap 47 , but here is the circumferential groove 46 as a chamfer inside the top of the bearing bush 14a is formed and is by means of a connection channel 49 with the upper mouth of the recirculation channel 28 connected. Preferably, the connection channel 49 not formed circumferentially.

LIST OF REFERENCE NUMBERS

10

baseplate

12

wave

12a

T-shaped section

14

rotor component

14a

bearing bush

16

fixed bearing component

18

annular bearing component

18a

radial section

18b

hollow cylindrical section

20

bearing gap

22a, b

radial bearings

24

separator gap

26

thrust

27

gap

28

recirculation

30

cap

32

seal gap

34

seal gap

36

pump seal

36a

groove structures

37, 137

groove

38

axis of rotation

40

ferromagnetic ring

42

stator

44

rotor magnet

46

groove

47

Gap, radial

47a

Gap, radial

48

area

48a

stop surface

49

connecting channel

50, 150

grooves

52

thrust

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 102008031618 A1 [0003]
• DE 102011025369 A1 [0008]
• US 2010/0296190 A1 [0009]

Claims (25)

Fluid dynamic bearing system, in particular for rotational mounting of a spindle motor, with a first stationary bearing component, which at least one shaft arranged in a bearing bore (US Pat. 12 ), a shaft receiving stationary bearing component ( 16 ) and arranged on the shaft annular bearing member ( 18 ), and a second rotatable bearing component, which at least one rotor component ( 14 ) with a bearing bush ( 14a ), wherein the two bearing components by a bearing fluid filled with a bearing gap ( 20 ) separated by two axially spaced fluid dynamic radial bearings ( 22a . 22b ) and at least one fluid dynamic thrust bearing ( 26 ) are rotatably mounted relative to each other, wherein the bearing gap ( 20 ) has two open ends through seal gaps ( 32 . 34 ) are sealed, and the bearing bush ( 14a ) a substantially radially extending annular surface ( 48 ) formed with an opposite surface of the annular bearing component ( 18 ) a radially extending annular gap ( 47 ) forming the bearing gap ( 20 ) with a first sealing gap ( 32 ), characterized in that in a radially outer portion of the annular gap ( 47 ) in the annular area ( 48 ) of the bearing bush ( 14a ) or in the opposite surface of the annular bearing component ( 18 ) a circumferential groove ( 46 ) is provided. Fluid dynamic bearing system according to claim 1, characterized in that the circumferential groove ( 46 ) in the axial direction has a depth which is at least six times as large as the axial height of the annular gap ( 47 ). Fluid dynamic bearing system according to claim 1, characterized in that the circumferential groove ( 46 ) in the axial direction has a depth which is at least ten times as large as the axial height of the annular gap ( 47 ). Fluid dynamic bearing system according to one of claims 1 to 3, characterized in that the axial height of the annular gap ( 47 ) in the operation of the bearing between 15 microns and 25 microns. Fluid dynamic bearing system according to claim 1, characterized in that the circumferential groove ( 46 ) in the axial direction has a depth of at least 10 microns. Fluid dynamic bearing system according to one of claims 1 to 5, characterized in that the circumferential groove ( 46 ) has a width of at least 100 microns in the radial direction Fluid dynamic bearing system according to one of claims 1 to 6, characterized in that a in the bearing bush ( 14a ) extending recirculation channel ( 28 ) in the region of the annular gap ( 47 ) ends. Fluid dynamic bearing system according to one of claims 1 to 7, characterized in that the diameter of the recirculation channel ( 28 ) at least 40% of the radial extent of the annular surface ( 48 ) is. Fluid dynamic bearing system according to one of claims 1 to 8, characterized in that the recirculation channel ( 28 ) at least partially into the groove ( 46 ) opens. Fluid dynamic bearing system according to one of claims 1 to 8, characterized in that the recirculation channel ( 28 ) by means of a connection channel ( 49 ) with the circumferential groove ( 46 ), wherein the axial height of the connecting channel ( 49 ) is greater than the axial height of the annular gap ( 47 ). Fluid dynamic bearing system according to one of claims 9 or 10, characterized in that the recirculation channel ( 28 ) by an angle between 3 degrees and 20 degrees relative to the rotation axis ( 38 ) is inclined, wherein a first opening of the recirculation channel ( 28 ) in the region of the annular gap ( 47 ) a smaller distance to the axis of rotation ( 38 ), as a second opening of the recirculation channel ( 28 ), which in the region of a radially extending gap ( 27 ), wherein the radially extending gap ( 27 ) between the thrust bearing ( 26 ) as well as the sealing gap ( 34 ) is arranged. Fluid dynamic bearing according to one of claims 1 to 11, characterized in that within the surface ( 48 ) a radially extending abutment surface ( 48a ) is provided, wherein only in the area of the stop surface ( 48a ) a narrow gap between the annular bearing component ( 18 ) and the bearing bush ( 14a ) remains. Fluid dynamic bearing according to claim 12, characterized in that the extension of the stop surface ( 48a ) in the radial direction less than two-thirds of the extent of the surface ( 48 ) in the radial direction. Fluid dynamic bearing according to one of claims 12 or 13, characterized in that the upper opening of the recirculation channel ( 28 ) at least partially in the stop surface ( 48a ) opens. Fluid dynamic bearing system according to one of claims 12 to 14, characterized in that a in the bearing bush ( 14a ) running Recirculation channel ( 28 ) completely in the area of the stop surface ( 48a ) and that the recirculation channel ( 28 ) only over the radially extending gap ( 47 ) with the circumferential groove ( 46 ) connected is. Fluid dynamic bearing system according to one of claims 1 to 15, characterized in that the first sealing gap ( 32 ) by adjoining surfaces of the annular bearing component ( 18 ) and the bearing bush ( 14a ) is formed, wherein on the first sealing gap ( 32 ) limiting surface of the annular bearing component ( 18 ) or the bearing bush ( 14a ) at least one groove ( 37 . 137 ) which is perpendicular or at an angle> 0 ° with respect to the axis of rotation ( 38 ) runs. Fluid dynamic bearing system according to one of claims 1 to 16, characterized in that along the first sealing gap ( 32 ) a dynamic pump seal ( 36 ) with pump groove structures ( 36a ), wherein the pump groove structures ( 36a ) in a rotation of the bearing one in the direction of the first radial bearing ( 22a ) directed pumping action on the in the sealing gap ( 32 ) produce bearing fluid. Fluid dynamic bearing system according to one of claims 1 to 17, characterized in that the groove ( 37 ) a part of the pump groove structures ( 36a ) of the pumping seal ( 36 ). Fluid dynamic bearing system according to one of claims 1 to 18, characterized in that the groove ( 37 . 137 ) has a greater depth and / or a greater length and / or a greater width than the pump groove structures ( 36a ). Fluid dynamic bearing system according to one of claims 1 to 19, characterized in that on a radially inner portion of the annular surface ( 48 ) a plurality of radially extending or obliquely to the radius grooves ( 50 . 150 ) are provided. Fluid dynamic bearing system according to claim 20, characterized in that the grooves ( 50 . 150 ) have a greater depth and / or a greater length and / or a greater width than the pump groove structures ( 36a ). Fluid dynamic bearing system according to one of claims 20 and 21, characterized in that the obliquely to the radius grooves ( 50 ) surface ( 48 ) together with a lower end face of the annular bearing component ( 18 ) a second fluid dynamic thrust bearing ( 52 ). Fluid dynamic bearing system according to one of claims 20 or 22, characterized in that the obliquely to the radius grooves ( 50 ) in a rotation of the bearing one in the direction of the first radial bearing ( 22a ) directed pumping action on the bearing fluid. Spindle motor with a fluid dynamic bearing system according to one of claims 1 to 23. A hard disk drive hard disk drive according to claim 24, which rotatively drives at least one disk, and has a write-read device for writing and reading data to and from the disk.

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