DE102011106511A1 - Fluid-dynamic bearing system for spindle motor for e.g. 2.5 inch hard disk drive for laptop, has bearing component arranged at shaft, where ratio of length of shaft and mutual distance between radial bearings is larger than specified value - Google Patents

Abstract

The system has an annular bearing component (18) arranged at a shaft (12), which is received in a central bore of a stationary bearing component (16). The components are separated from each other by a bearing gap (20) that is filled with bearing fluid i.e. bearing oil. The components are rotatably mounted relative to each other by axially spaced apart fluid-dynamic radial bearings (22a, 22b) and a fluid dynamic thrust bearing (26). A ratio of length (lW) of the shaft and mutual distance (sL) between the radial bearings is larger than 2.6, preferably 3.0. An independent claim is also included for a hard disk drive.

Description

Field of the invention

The invention relates to a fluid dynamic bearing system, as used for example for the rotary mounting of spindle motors. Spindle motors with fluid dynamic bearing system u. a. used to drive hard disk drives or fans.

State of the art

A fluid dynamic bearing system generally consists of a fixed bearing component and a movable bearing component, which are separated by a bearing gap filled with a bearing fluid and rotatably supported about a common axis of rotation relative to each other. In a known manner, bearing surfaces are provided which are provided with bearing groove structures 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 each other, the bearing groove structures exert a pumping action on the bearing fluid in the bearing gap and 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. As a stationary bearing component, this bearing system comprises a shaft which is held in a bore of a further stationary bearing component. A movable bushing, which is part of a rotor component, rotates about the fixed shaft. The bearing system comprises two fluid dynamic radial bearings arranged at an axial distance from one another and at least one magnetically biased fluid dynamic axial 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. For example, a bearing of the type described for a spindle motor for driving a typical 2.5 inch hard disk drive has a shaft of about 2.5 mm diameter. For example, with a 3.5-inch hard disk drive, the shaft has a diameter of about 4 mm.

Modern hard disk drives are very small in size so they can fit in the ever-shrinking electronic devices. In particular, a low height is sought in order to realize very flat laptops and other devices. By reducing the height of the hard disk drives, the maximum height of the fluid dynamic bearing system and in particular the bearing distance of the radial bearings are limited. However, a small bearing distance is at the expense of the bearing stiffness, in particular the Kippfestigkeit the camp. You can not increase the storage distance within the available height arbitrarily, because this is the available area for applying the Lagerrillenstrukturen too small. For optimization of the tilting rigidity, therefore, the length of the shaft (which roughly corresponds to the overall height of the bearing), the bearing distance and the available bearing surface of the radial bearings must be optimized.

Disclosure of the invention

It is the object of the invention to specify a fluid-dynamic bearing system which has improved rigidity against tilting.

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

A spindle motor with the fluid dynamic bearing system according to the invention and a hard disk drive, which is driven by such a spindle motor, are the subject of the independent claims.

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

The described fluid dynamic bearing system comprises a first bearing component, which has at least one bearing bush with a bearing bore, and a second bearing component which has at least one shaft arranged in the bearing bore, a stationary bearing component receiving the shaft and an annular bearing component arranged on the shaft. The first and the second bearing component are separated from one another by a bearing gap filled with a bearing fluid and are rotatably mounted relative to one another by means of two fluid-dynamic radial bearings spaced apart axially from one another and at least one fluid-dynamic axial bearing. The shaft has a length l _w and the fluid dynamic radial bearings have a mutual bearing distance s _L on. The latter is determined as the distance of the apexes of the respective radial bearings from each other.

According to the invention, the ratio between the length l _{W of} the shaft and the bearing distance s _{L is} greater than 2.6.

This inventive ratio between the length of the shaft and the bearing distance of greater than 2.6 ensures that, on the one hand, a relatively large bearing distance is realized relative to the length of the shaft and on the other hand, the bearing distance but not too large, so still enough available storage space for applying the Lagerrillenstrukturen the radial bearings remains. Forced storage of bearings with very low height of the storage space must also be very small, so that the storage space can be sized sufficiently large. The storage system according to the invention can be used in particular for the rotary storage of spindle motors for driving 2.5 or 3.5 inch hard disk drives.

In order to further increase the tilt stability, it is advantageous according to the invention to adapt the diameter of the annular bearing component to the bearing spacing s _L. It has proven particularly advantageous if the ratio between the diameter d of the annular bearing component and the bearing spacing s _{L is} greater than 1.0.

This is based on the fact that according to the invention adjacent surfaces of the annular bearing member and the bearing bush or a hub connected to the bearing bushing define a first, filled with bearing fluid sealing gap, which is connected to the bearing gap. Along an axially extending section of this first sealing gap, in a preferred embodiment of the invention, a dynamic pumping seal with pumping groove structures is arranged. The pumping groove structures generate during a rotation of the bearing directed in the direction of the first radial bearing pumping action on the bearing fluid located in the sealing gap.

The pumping groove structures of the pumping seal are preferably arranged on a peripheral surface of the annular bearing component delimiting the first sealing gap.

The diameter d of the annular bearing component, the width of the sealing gap and the shape of the pump groove structures significantly determine the effectiveness of the dynamic pumping seal. With a sufficiently large diameter of the annular member, the pumping seal acts as part of a fluid dynamic radial bearing.

The two fluid dynamic radial bearings are formed by opposing bearing surfaces of the shaft and the bearing bore of the bearing bush and have radial bearing grooves. A first radial bearing is formed substantially symmetrically and comprises a circumferential line substantially symmetrical radial bearing grooves.

The dynamic pumping seal along the first sealing gap supplements the effect of this first radial bearing, so that the rigidity of the bearing is improved overall.

A second radial bearing is arranged at an axial distance from the first radial bearing and is asymmetrical. It comprises radial bearing grooves, which have asymmetrical lengths of the bearing grooves relative to a circumferential line passing through the apex, which generate a pumping action directed predominantly in the direction of the first radial bearing on the bearing fluid in the bearing gap during rotation of the bearing.

The other side of the bearing gap is sealed by a second sealing gap connected to the bearing gap. The second sealing gap is formed by adjacent surfaces of the bearing bush and the fixed bearing component or a fixed bearing ring arranged in the fixed bearing component.

A stabilization of the bearing in the axial direction is achieved by a first fluid-dynamic thrust bearing, which is arranged in a radial portion of the bearing gap, which is located between an upper end side of the fixed bearing member or a bearing ring connected to this bearing member and an opposite end face of the bearing bush.

The first fluid-dynamic thrust bearing may be magnetically biased, or it may be additionally or alternatively provided a second fluid-dynamic thrust bearing, which is arranged between an upper end side of the bearing bush and the annular bearing member connected to the shaft. The second fluid dynamic thrust bearing acts opposite to the first fluid dynamic thrust bearing. Both thrust bearings preferably have spiral-shaped bearing grooves which pump the bearing fluid radially inwards.

So that a continuous circulation of the bearing fluid is ensured in the bearing gap, a recirculation passage is preferably arranged in the bearing bush, which connects the radially extending portion of the first sealing gap with the radial portion of the second sealing gap.

Hereinafter, a preferred embodiment of the invention will be described with reference to drawing figures. This results in further features and advantages of the invention.

Brief description of the drawings

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

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

Description of preferred embodiments of the invention

1 shows a spindle motor with a fluid dynamic bearing according to a first preferred embodiment of the invention. Such a spindle motor can be used, for example, to drive storage disks in a 2.5-inch 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 includes a central bore in which a shaft 12 is attached. The wave 12 has a total length l _w of, for example, l _w = 8.35 mm and a diameter of, for example, 2.5 mm. At the other, free end of the fixed shaft 12 is an annular component 18 arranged, preferably in one piece with the shaft 12 is formed and whose diameter is for example d = 4.2 mm. The named components 10 . 12 . 16 and 18 form the fixed component of the spindle motor. The bearing comprises a rotor component with a bearing bush 14 and a hub formed integrally with the bearing bush 48 , The bearing bush 14 of the rotor component is in one through the shaft 12 and the two components 16 . 18 formed intermediate space is rotatably arranged relative to these components. The annular component 18 is in a corresponding annular recess of the rotor component 14 . 48 arranged. Adjacent surfaces of the shaft 12 , the rotor component 14 and the two bearing components 16 . 18 are by a bearing gap open on both sides 20 separated from each other. The bearing gap 20 is filled with a bearing fluid, such as a bearing oil. The annular bearing component 18 serves inter alia as a stopper component, which is the rotor component 14 . 48 prevents it from falling out even in the overhead position of the bearing.

The bearing bush 14 of the rotor component has a cylindrical bore, on whose inner circumference two cylindrical radial bearing surfaces are formed, which by a relatively narrow separating gap between them 24 are separated. The radial bearing surfaces surround the standing wave 12 at a radial distance of a few microns to form an axially extending portion 20a of the storage gap 20 , The bearing surfaces are provided with suitable bearing grooves, so that they each with opposite bearing surfaces of the shaft 12 two fluid dynamic radial bearings arranged at an axial distance from one another 22a and 22b form. The bearing distance of the two radial bearings 22a . 22b For example, s _L = 1.83 mm.

According to the invention, it is required that the ratio between the length l _{W of} the shaft and the bearing spacing s _{L is} greater than 2.6. In the present embodiment: l _W / s _L = 8.35 mm / 1.83 mm = 4.56, ie significantly more than the required value. Further, it is advantageous if the ratio of the diameter d of the annular bearing member and the bearing distance s _{L is} greater than 1. In the present embodiment is: d / s _L = 4.2 mm / 1.83 mm = 2.3.

The first radial bearing 22a is preferably symmetrical and produces a uniform pumping action on the bearing fluid in both directions of the bearing gap 20 while the second radial bearing 22b is preferably formed asymmetrically and a predominantly in the direction of the first radial bearing 22a directed pumping action generated. The radial bearing grooves of the two radial bearings 22a and 22b are preferably sinusoidal or herringbone grooves or V-shaped.

To the vertically extending portion of the bearing gap below the second radial bearing 22b closes a radially extending section 20b of the storage gap 20 at. This radially extending portion of the bearing gap 20 is by radially extending bearing surfaces on the end face of the bearing bush 14 and corresponding opposite bearing surfaces of the fixed bearing component 16 educated. The radially extending bearing surfaces form a fluid dynamic thrust bearing 26 in the form of a to the axis of rotation 44 vertical circular ring. The fluid dynamic thrust bearing 26 is for example characterized by helical bearing grooves, which are either on the front side of the bearing bush 14 , the front side of the fixed bearing component 16 or on both parts.

In a radially outer region of the fixed bearing component 16 and / or the opposite bearing bush 14 in which a recirculation channel 28 opens, an axially distributed, annular gap portion may be provided to the bearing friction of the thrust bearing 26 to reduce.

In a preferred embodiment of the invention are all for the radial bearings 22a . 22b and the thrust bearing 26 and possibly a pump seal 36 necessary bearing or pump groove structures on the corresponding surfaces of the bearing bush 14 arranged what the manufacture of the warehouse, especially the wave 12 and the two components 16 . 18 simplified.

Following the upper radial bearing 22a is the rotor component 14 . 48 designed such that it forms a radially extending surface, which with a corresponding opposite radial surface of the annular bearing member 18 a radial section 32a a first sealing gap 32 forms. To the radial gap section 32a closes an axially extending section 32b of the first sealing gap 32 which terminates the fluid bearing system at this end. The first sealing gap 32 is formed by opposing surfaces of the rotor component 14 . 48 and the annular member 18 limited widened at the outer end in an annulus 33 preferably with a conical cross section. The conical annulus 33 in which the axial section 32b the sealing gap 32 opens, on the one hand serves as a filling reservoir for filling the bearing fluid in the bearing and as a compensating volume for the bearing fluid and on the other hand as a conical capillary seal. This conical annulus 33 is from a cap 30 covered.

Along the axial section 32b the sealing gap 32 is a pump seal 36 with pump groove structures 36a arranged. The pump groove structures 36a are preferably on an inner circumferential surface of the rotor component 14 . 48 arranged; but they can also alternatively or additionally on a sealing gap 32 limiting outer surface of the annular bearing component 18 be arranged. The pump groove structures 36a are shaped so that when the bearing is rotated, it will pump in the section 32b the sealing gap 32 produce stored bearing fluid. The pumping action is in the direction of the bearing gap 20 directed into the camp interior. The ends of the pump groove structures 36a preferably do not extend to the ends of the axial section 32b the sealing gap 32 , Rather, it is between the end of the pump groove structures 36a and the upper end of the axial section 32b the sealing gap 32 provided a defined distance, whereby the shock resistance of the bearing is improved. Furthermore, it can be provided, the width of the axial section 32b between the end of the pump groove structures 36a and the outer end of the axial section 32b the sealing gap 32 To design less than about the gap width in the pump seal 36 , Furthermore, the area between the end of the pump groove structures 36a and the outer end of the axial section 32b the sealing gap 32 be designed at least partially as a conical capillary seal with a small opening angle of about 2 degrees.

The ends of the pump groove structures 36a do not break into the area of the conical annulus 33 through, but the sealing gap is at the end of its axial section 32b at the transition to the conical annulus 33 relatively narrow, preferably between 5 to 20 microns. The depth of pump groove structures 36a is also about 5 to 20 microns.

A cap 30 closes the first sealing gap 32 and the annulus 33 , The cap 30 is on a circumferential edge 14b the hub 48 or the bearing bush 14 held and there, for example, glued, pressed and / or welded. The inner edge of the cap 30 can together with the outer circumference of the annular bearing component 18 or the shaft 12 form a gap seal. This increases the safety against leakage of bearing fluid from the first sealing gap 32 ,

Under normal operating conditions of the bearing, the bearing fluid is within the first sealing gap 32 ; When the bearing is at a standstill, the bearing fluid fills part of the conical annular space 33 out.

At the radial portion of the bearing gap 20 in the area radially outside the thrust bearing 26 closes a proportionately filled with bearing fluid second sealing gap 34 on, by opposing surfaces of the bearing bush 14 and the fixed bearing component 16 is formed. The second sealing gap 34 seals the bearing gap 20 off on this page. The second sealing gap 34 runs approximately parallel to the axis of rotation 44 and widens conically towards the end. The second sealing gap 34 is from an outer peripheral surface of the bearing bush 14 the rotor member and an inner peripheral surface of the fixed bearing member 16 limited. In addition to the function as a capillary seal, the second 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 second sealing gap 34 forming surfaces on the rotor component 14 . 48 and the fixed bearing component 16 can each relative to the axis of rotation 44 be inclined at least partially inwards. As a result, the bearing fluid in a rotation of the bearing due to the centrifugal force in the bearing interior in the direction of the bearing gap 20 pressed.

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 rotor magnet surrounding the stator assembly at a distance 40 attached to an inner circumferential surface of the hub 48 is arranged. In principle it is possible, the bearing bush 14 as a separate part of the hub 48 train.

In the case that the spindle motor only a single fluid dynamic thrust bearing 26 has, during operation of the motor, a force on the movable bearing parts in the direction of the fixed bearing component 18 generated, a corresponding axial counterforce or biasing force must be provided on the movable bearing part, which holds the bearing system axially in equilibrium. For this, the base plate 10 a ferromagnetic ring 38 have, the rotor magnet 40 axially opposite and is magnetically attracted by this. This magnetic attraction acts in operation against the force of the thrust bearing 26 and keeps the bearing axially stable. Alternatively or in addition to this solution, a so-called "magnetic offset" can be used by the stator assembly 42 and the rotor magnet 40 axially offset from each other, in such a way that the magnetic center of the rotor magnet 40 axially further away from the base plate 10 is arranged as the magnetic center of the stator assembly 42 , Even with this measure, an axial force is built up by the magnet system of the motor, which is opposite to the thrust bearing 26 acts.

In order to ensure a continuous flushing of the storage system with bearing fluid, in a known manner, a recirculation channel 28 intended. The recirculation channel 28 is inventively as axially or slightly obliquely extending channel in the bearing bush 14 formed of the rotor component, which is preferably at an acute angle with respect to the axis of rotation 44 of the warehouse is arranged. The recirculation channel 28 connects the two radial sections of the bearing gap 20 between the storage areas and the sealing areas directly to each other. Due to the directed pumping action of the bearing groove structures of the thrust bearing 26 and the radial bearing 22b results in the radial bearing gap 20 preferably a flow in the direction of the upper radial bearing 22a which - supported by centrifugal forces due to the oblique arrangement of the recirculation channel 28 - Through the recirculation channel down in the direction of the thrust bearing 26 flows back, so that sets a cycle. In addition, the bearing fluid in the recirculation channel 28 due to the effect of centrifugal force in the inclined channel downwards in the direction of the thrust bearing 26 promoted, so that sets a stable fluid circuit.

2 shows a spindle motor with a fluid dynamic bearing according to a second preferred embodiment of the invention, as it can be used to drive storage disks, such as a 3.5-inch hard disk drive.

The spindle motor comprises a base plate 110 having a cylindrical opening in which a fixed bearing member 116 is included. The fixed bearing component 116 includes a central bore in which a shaft 112 is attached. The wave 112 has a diameter of, for example, 4 mm and a length of, for example, l _W = 22.73 mm. At the other, free end of the fixed shaft 112 is an annular component 118 arranged here in two parts with the shaft 112 is trained. The diameter of the annular component is, for example, d = 7.8 mm. The named components 110 . 112 . 116 and 118 form the fixed component of the spindle motor. The storage system further comprises a bearing bush 114 in one by the shaft 112 and the two components 116 . 118 formed intermediate space is rotatably arranged relative to these components. The annular component 118 is in a recess of a hub 148 arranged. The hub 148 is on the outer circumference of the bearing bush 114 attached. The hub 148 and the bearing bush 114 can, as shown, consist of two parts, but of course also of a single part. Adjacent surfaces of the shaft 112 , the bearing bush 114 and the two components 116 . 118 are by a bearing gap open on both sides 120 separated from each other. The bearing gap 120 is filled with a bearing fluid, such as a bearing oil.

The bearing bush 114 has in the direction of the fixed bearing component 116 a sleeve-shaped section 114a and a continuous cylindrical bore, on whose inner circumference two cylindrical radial bearing surfaces are formed. The radial bearing surfaces of the bearing bush 114 enclose the standing wave 112 at a distance of a few microns to form an axially extending portion 120a of the storage gap 120 , The radial bearing surfaces of the bearing bush 114 are provided with suitable bearing grooves, so that they each with opposite bearing surfaces of the shaft 112 two fluid dynamic radial bearings 122a and 122b form. The radial bearings 122a . 122b are through an intervening Separatorspalt 124 that has a larger gap distance than the radial bearing gap 120 , separated. A first radial bearing 122a is between the bushing 114 and the wave 112 educated. The bearing bush 114 ends here directly above the first radial bearing 122a , The second radial bearing 122b is also between the bushing 114 and the wave 112 formed and extends partially along the sleeve-shaped portion 114a the bearing bush 114 , The bearing distance of the two radial bearings 122a . 122b For example, s _L = 6.5 mm.

According to the invention, it is required that the ratio between the length l _{W of} the shaft and the bearing spacing s _{L is} greater than 2.6. In the present Embodiment is: l _W / s _L = 22.73 mm / 6.5 mm = 3.5, ie significantly more than the required value. Further, it is advantageous if the ratio of the diameter d of the annular bearing member and the bearing distance s _{L is} greater than 1. In the present embodiment is: d / s _L = 7.8 mm / 6.5 mm = 1.2.

An annular end face of the sleeve-shaped portion 114a the bearing bush 114 forms with a surface DLC-coated, hollow cylindrical, fixed bearing plate 125 a radially extending portion 120b the bearing gap, which is a continuation of the axial section 120a of the storage gap 120 represents and is filled with bearing fluid. The bearing plate 125 includes the wave 112 and is itself from the fixed bearing component 116 includes.

The radially extending surfaces of the sleeve-shaped portion 114a the bearing bush and the bearing plate 125 form a fluid dynamic thrust bearing 126 in the form of a to the axis of rotation 144 vertical circular ring. The fluid dynamic thrust bearing 126 is for example characterized by helical bearing grooves, which are either on the front side of the first sleeve-shaped portion 114a , the front side of the fixed bearing plate 125 or can be mounted on both parts and the bearing fluid radially inward toward the axis of rotation 144 pump.

For sealing the upper end of the bearing gap 120 is a first sealing gap 132 provided, which is formed by a radially extending portion 132a between an end face of the bearing bush 114 and a bottom of the annular member 118 and an axially extending portion 132b between an outer peripheral surface of the annular member 118 and an inner circumferential surface of the hub 148 , The first sealing gap 132 widens at the outer end into an annulus 133 preferably with a conical cross section. The hub 148 points radially outward of the radial section 132a of the first sealing gap 132 a step up on the front of the bearing bush 114 rests, leaving the hub 148 relative to the bearing bush 114 is precisely positioned. The fixed bearing component 116 is in a corresponding recess of the base plate 110 arranged.

In the radial section 132a of the first sealing gap 132 is preferably a second thrust bearing 127 arranged, which is formed by spiral or herringbone-like bearing grooves, which the bearing fluid in the bearing interior in the direction of the adjacent radial bearing 122a pump. In addition, a magnetic offset is provided here by the rotor magnet 140 from its magnetic center relative to the stator assembly 142 arranged offset axially upwards. A cap 130 closes the first sealing gap 132 , The cap 130 is at one stage of the bearing bush 114 held and there, for example, glued, pressed and / or welded. The inner edge of the cap 130 can be together with the outer circumference of the shaft 112 form a gap seal. This increases the safety against leakage of bearing fluid from the first sealing gap 132 , However, under normal operating conditions and also when the bearing is at a standstill, the bearing fluid is located within the largely axially extending sealing gap 132 ,

To the radially extending section 120b of the storage gap 120 , where the first thrust bearing 126 is arranged, an axially extending section closes 134a a second sealing gap 134 which is filled with bearing fluid. Along this axially extending section 134a the second sealing gap 134 are groove structures of a dynamic pump seal 137 preferably on an outer peripheral surface of the sleeve-shaped portion 114a the bearing bush 114 arranged. An inner circumferential surface of the fixed bearing component 116 is the outer peripheral surface of the first sleeve-shaped portion 114a the bearing bush 114 across from. The groove structures of the dynamic pump seal 137 create a pumping action on that in the gap section 134a located bearing fluid in the direction of the bearing interior, ie in the direction of the radial bearing 122b ,

To the vertical section 134a the second sealing gap 134 closes a likewise filled with bearing fluid, relatively short radially extending portion 134b the sealing gap 134 at. This radially extending section 134b of the second sealing gap 134 is by a radially extending surface of the bearing bush 114 and an opposing surface of the fixed bearing member 116 limited.

At the short radial section 134b of the second sealing gap 134 closes a proportionally filled with bearing fluid axial section 134c of the second sealing gap 134 on, passing through an outer peripheral surface of the bearing bush 114 and an inner peripheral surface of the fixed bearing member 116 is limited. The axial section 134c the second sealing gap 134 forms a conical capillary seal, complements the pump seal 137 and seals the bearing gap 120 off at this end. The axial section 134c of the second sealing gap 134 runs approximately parallel to the axis of rotation 144 and widens conically towards the end. In addition to the function as a capillary seal, the second sealing gap is used 134 as a whole 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 the conical section 134c of the second sealing gap 134 forming surfaces of the bearing bush 114 and the fixed bearing component 116 can each relative to the axis of rotation 144 be inclined at least partially 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 120 pressed. Due to the axial recess of the fixed bearing component, the second sealing gap 134 According to the invention be formed relatively long. As a result, the sealing effect of the second sealing gap 134 and consequently improves the shock resistance of the bearing.

Along the axial section 132b the sealing gap 132 is a pump seal 136 with pump groove structures 136a arranged. The pump groove structures 136a are preferably on an inner circumferential surface of the rotor component 148 arranged; but they can also alternatively or additionally on a sealing gap 132 limiting outer surface of the annular bearing component 118 be arranged. The pump groove structures 136a are shaped so that when the bearing is rotated, it will pump in the section 132b the sealing gap 132 produce stored bearing fluid. The pumping action is in the direction of the bearing gap 120 directed into the camp interior.

In a preferred embodiment of the invention are all for the radial bearings 122a . 122b and the thrust bearing 126 and possibly the pump seal 137 necessary bearing or pump groove structures on the corresponding surfaces of the bearing bush 114 arranged what the manufacture of the bearing, especially the shaft 112 and the two components 116 . 118 simplified.

The electromagnetic drive system of the spindle motor is formed in a known manner by a on the base plate 110 arranged stator arrangement 142 and an annular permanent magnet surrounding the stator assembly at a radial distance 140 , the one with a surrounding return ring 146 on an inner circumferential surface of the hub 148 is arranged and serves as a rotor magnet for driving the electric motor.

In order to ensure a continuous flushing of the storage system with bearing fluid, in a known manner, a recirculation channel 128 intended. The recirculation channel 128 is according to the invention as an axial or slightly oblique to the axis of rotation 144 extending channel in the bearing bush 114 formed, preferably at an acute angle with respect to the axis of rotation 144 of the warehouse is arranged. The recirculation channel 128 connects the radial section 132a of the first sealing gap 132 with the radial section 134b of the second sealing gap 134 , The bearing fluid is in the oblique recirculation channel 128 due to the effect of centrifugal force down towards the second

seal gap 134 conveyed and circulated through the radial and axial section 120b and 120a of the storage gap 120 upwards and through radial section 132a the first sealing gap 132 back, so that sets a stable fluid circuit in the camp.

Between the outer periphery of the upper edge of the fixed bearing component 116 and an inner periphery of a downwardly facing, annular neck of the hub 148 there is a narrow gap 129 which is not filled with bearing fluid and which extends in the axial direction. The gap 129 serves as a vapor barrier and prevents escape of evaporated bearing fluid from the second sealing gap 134 , which increases the life of the bearing.

LIST OF REFERENCE NUMBERS

10, 110

baseplate

12, 112

wave

14, 114

bearing bush

114a

sleeve-shaped section

14b

surrounding border

16, 116

fixed bearing component

18, 118

annular bearing component

20, 120

the bearing gap

20a, 120a

axial section of the bearing gap

20b, 120b

radial section of the bearing gap

22a, b; 122a, b

radial bearings

24, 124

separator gap

125

bearing plate

26, 126

thrust

127

thrust

28, 128

recirculation

129

gap

30, 130

cap

32, 132

first sealing gap

32a, 132a

radial section

32b, 132b

axial section

33, 133

conical annulus

34, 134

second sealing gap

134a, 134c

axial portion of the sealing gap

134b

radial section of the sealing gap

36, 136

pump seal

36a, 136a

groove structures

137

pump seal

38

ferromagnetic ring

40, 140

rotor magnet

42, 142

stator

44, 144

axis of rotation

146

Return ring

48, 148

hub

d

Diameter of the annular bearing component

l _W

Length of the shaft

s _L

Bearing clearance of radial bearings

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102008031618 A1 [0003]

Claims (15)

Fluid dynamic bearing system, in particular for the rotary mounting of a spindle motor, with a first bearing component, which has at least one bearing bush ( 14 ; 114 ) with a bearing bore, and a second bearing component, which has at least one shaft arranged in the bearing bore ( 12 ; 112 ), a shaft receiving stationary bearing component ( 16 ; 116 ) and arranged on the shaft annular bearing member ( 18 . 118 ), wherein the first and the second bearing component by a filled with a bearing fluid bearing gap ( 20 ; 120 ) separated by two axially spaced fluid dynamic radial bearings ( 22a . 22b ; 122a . 122b ) and at least one fluid dynamic thrust bearing ( 26 ; 126 ) are rotatably mounted relative to each other, wherein the shaft ( 12 ; 112 ) has a length l _w , and the fluid dynamic radial bearings ( 22a . 22b ; 122a . 122b ) have a mutual bearing distance s _L , characterized in that the ratio between the length l _{w of} the shaft ( 12 ; 112 ) and the bearing distance s _{L is} greater than 2.6. Fluid dynamic bearing system according to claim 1, characterized in that the ratio between the length l _{W of} the shaft ( 12 ; 112 ) and the bearing distance s _{L is} greater than 3.0. Fluid dynamic bearing system according to claim 1 or 2, characterized in that the annular bearing component ( 18 ; 118 ) has a diameter d, wherein the ratio between the diameter d of the annular bearing component ( 18 ; 118 ) and the bearing distance s _{L is} greater than 1.0. Fluid dynamic bearing system according to one of claims 1 to 3, characterized in that adjacent surfaces of the annular bearing component ( 18 ; 118 ) and the bearing bush ( 14 ; 114 ) or a hub connected to the bearing bush ( 148 ) a first, filled with bearing fluid sealing gap ( 32 ; 132 ), which is connected to the bearing gap. Fluid dynamic bearing system according to claim 4, characterized in that along an axially extending portion ( 32b ; 132b ) of the first sealing gap ( 32 ; 132 ) a dynamic pump seal ( 36 ; 136 ) with pump groove structures ( 36a ; 136a ), wherein the pumping groove structures generate a pumping action directed in the direction of the first radial bearing on the bearing fluid in the sealing gap during a rotation of the bearing. Fluid dynamic bearing system according to claim 5, characterized in that the pump groove structures ( 36a ; 136a ) of the pumping seal ( 36 ; 136 ) on a first sealing gap ( 32 ; 132 ) limiting inner circumferential surface of the bearing bush ( 14 ) or the hub ( 148 ) are arranged. Fluid dynamic bearing system according to one of claims 1 to 6, characterized in that the fluid dynamic radial bearings ( 22a . 22b ; 122a . 122b ) by opposing bearing surfaces of the shaft ( 12 ; 112 ) and the bearing bore of the bearing bush ( 14 ; 114 ) are formed and have radial bearing grooves. Fluid dynamic bearing system according to one of claims 1 to 7, characterized in that a first radial bearing ( 22a . 122a ) is formed substantially symmetrically and comprises a circumferential line substantially symmetrical radial bearing grooves. Fluid dynamic bearing system according to one of claims 1 to 8, characterized in that a second radial bearing ( 22b ; 122b ) is formed substantially asymmetrically and comprises a circumferential line substantially asymmetrically formed radial bearing grooves, which in a rotation of the bearing a predominantly in the direction of the first radial bearing ( 22a ; 122a ) directed pumping action on the bearing fluid in the bearing gap produce. Fluid dynamic bearing system according to one of claims 1 to 9, characterized in that connected to the bearing gap second sealing gap ( 34 ; 143 ) by adjacent surfaces of the bearing bush and the fixed bearing component ( 18 ) or a bearing ring arranged in the stationary bearing component ( 125 ) is formed. Fluid dynamic bearing system according to one of claims 1 to 10, characterized in that a first fluid dynamic thrust bearing ( 26 ; 126 ) in a radial section ( 20b ; 120b ) of the storage gap ( 20 ; 120 ) arranged between an upper end face of the fixed bearing component ( 16 ) or one with this bearing component ( 16 ) associated bearing ring ( 125 ) and an opposite end face of the bearing bush ( 14 . 114 ) is located. Fluid dynamic bearing system according to one of claims 1 to 11, characterized in that a second fluid dynamic thrust bearing ( 127 ) between an upper end face of the bearing bush ( 114 ) and with the shaft ( 12 ) associated annular bearing component ( 118 ) is arranged. Fluid dynamic bearing system according to one of claims 1 to 12, characterized in that a recirculation channel ( 28 . 228 ) is present, the the radially extending portion ( 32a ; 132a ) of the first sealing gap ( 32 . 132 ) with the radial Section ( 20b ) of the storage gap ( 20 ) or the radial section ( 134b ) of the second sealing gap ( 134 ) connects. Spindle motor with a fluid dynamic bearing system, which comprises: a first bearing component which has at least one bearing bush ( 14 ; 114 ) comprises a bearing bore, and a second bearing component, which at least one shaft arranged in the bearing bore ( 12 ; 112 ), a shaft receiving stationary bearing component ( 16 ; 116 ) and arranged on the shaft annular bearing member ( 18 . 118 ), wherein the first and the second bearing component by a filled with a bearing fluid bearing gap ( 20 ; 120 ) separated by two axially spaced fluid dynamic radial bearings ( 22a . 22b ; 122a . 122b ) and at least one fluid dynamic thrust bearing ( 26 ; 126 ) are rotatably mounted relative to each other, wherein the shaft ( 12 ; 112 ) has a length l _w , and the fluid dynamic radial bearings have a mutual bearing distance s _L , characterized in that the ratio between the length l _{W of} the shaft ( 12 ; 112 ) and the bearing distance s _{L is} greater than 2.6. A hard disk drive with a spindle motor according to claim 14, which rotatably drives at least one disk, and a write-read device for writing and reading data to and from the disk.

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