DE102009031219A1 - Spindle motor for driving hard disk drive, has magnetic prestress-generating unit generating magnetic force for bearing exclusively from components of drive system, where hydraulic and magnetic forces are directed in opposite direction - Google Patents

Abstract

The motor has a fluid-dynamic bearing system provided with radial bearings (18, 22) and an axial bearing (28), where axial hydraulic force (Fh) is generated during operation of the motor. A motor component is pivotably supported about a rotational axis (14) by the fluid-dynamic bearing system and is driven by an electromagnetic drive system. A magnetic prestress-generating unit generates magnetic force (Fm) for the axial bearing exclusively from components of the drive system. The hydraulic and magnetic forces are directed in opposite direction. An independent claim is also included for a hard disk drive including a writing and reading device for writing and reading data.

Description

Field of the invention

The The invention relates to a spindle motor with a fluid dynamic Storage system according to the preamble of the claim 1. Such spindle motors are used for example for driving Hard disk drives or fans used.

State of the art

The DE 10 2007 039 231 A1 discloses a spindle motor with a fluid dynamic bearing system having at least one fixed engine component and at least one by means of the bearing system about a rotational axis rotatably mounted engine component. The bearing system comprises at least one fluid-dynamic radial bearing and a fluid-dynamic thrust bearing. The rotatably mounted engine component is driven by an electromagnetic drive system. Since the spindle motor has only a single fluid-dynamic thrust bearing, which generates a unidirectional force component, means for generating a preload for the thrust bearing are present in a known manner, which generate a force acting opposite to the thrust bearing force. Preferably, a magnetic bias is used. For this purpose, the rotor magnet axially opposite a ferromagnetic ring which is fixed to the base plate of the motor. The ferromagnetic ring is attracted by the rotor magnet by a magnetic force acting in opposition to the force of the fluid dynamic thrust bearing. In addition to this arrangement, the rotor magnet may be axially offset relative to the stator assembly, upwardly in the direction of the fluid dynamic thrust bearing. Due to this axial offset results not only a radially acting magnetic force component, but also an axially acting magnetic force component, which is used in addition to the bias of the thrust bearing between the stator and the rotor magnet.

To the Drive hard drives with a 2.5-inch form factor are often spindle motors with a fluid dynamic thrust bearing and a combination of magnetic bias between the stator and the rotor magnet and the rotor magnet and the ferromagnetic Ring used. However, this ferromagnetic ring requires at the mounting an additional assembly step, where he usually glued to the base plate. This bond can work Loosen and the ring can block the engine. In addition caused the installation of a ferromagnetic ring not insignificant additional Costs.

Disclosure of the invention

It The object of the invention is a spindle motor with fluid dynamic Specify storage system, in particular for driving hard disk drives, for lower speeds and lower loads is designed and can be produced inexpensively.

These The object is achieved by a spindle motor solved according to the features of claim 1.

preferred Embodiments of the invention and further advantageous features emerge from the dependent claims.

Of the Spindle motor includes a fixed engine component and at least a rotatably mounted engine component, wherein the pivot bearing means a fluid dynamic bearing system takes place about a rotation axis. The storage system comprises at least one fluid dynamic radial bearing and a fluid dynamic thrust bearing. The rotatably mounted engine component is powered by an electromagnetic drive system.

According to the invention Means for generating a magnetic bias for the thrust bearing exists, consisting exclusively of components consist of the electromagnetic drive system.

Especially for low speeds, for example less than 4200rpm and low loads can when using at most two disks reduces the required axial bearing force and thus also the required strength for the magnetic preload. Therefore, according to the invention no ferromagnetic ring axially opposite the rotor magnet more necessary. This saving of the ferromagnetic ring saves accordingly Cost and installation effort and increases reliability of the motor, since a loosening of the ferromagnetic ring is not can happen more. The required axial preload is according to the invention exclusively by Applied components of the electromagnetic drive system. The electromagnetic drive system includes a stator assembly and a rotor magnet, wherein the magnetic center of the rotor magnet a having axial offset to the magnetic center of the stator assembly. This axial offset produces an axial magnetic force component which counteracts the thrust bearing and a magnetic bias of the thrust bearing forms.

The stationary motor component includes a base plate, a bearing bushing fixed in the base plate, and the stator assembly of the electromagnetic drive system. The rotatably mounted Mo Door component includes a recorded in the bearing bore of the bearing bushing, a shaft connected to the rotor member and a rotor mounted on the rotor member rotor magnet. According to another embodiment of the invention, the shaft may also be formed as a fixed shaft, wherein the bearing bush is rotatably mounted on the shaft.

Either the radial bearings and the thrust bearing have bearing surfaces on, by a filled with a bearing fluid bearing gap are separated from each other.

In A preferred embodiment of the invention are in particular two radially spaced radial bearings present, the by bearing surfaces of the associated Bearing bush and shaft formed and through bearing groove structures Marked are. The thrust bearing is preferably through each other associated bearing surfaces of the bearing bush and the rotor component or a first bearing component formed and by corresponding Lagerrillenstrukturen characterized.

Preferably is in the bearing bush a filled with bearing fluid recirculation channel arranged, the mutually remote portions of the bearing gap connects with each other. In particular, the recirculation channel connects a region of the bearing gap arranged adjacent to a stopper ring the bearing gap running in the region of the axial bearing.

An opening the recirculation channel opens into the area of the thrust bearing, wherein in a preferred embodiment of the invention, the opening of the Rezirkulationskanals through the bearing groove structures of the thrust bearing is not covered. In a preferred embodiment is the thrust bearing in its surface much smaller as the end face of the bearing bush, wherein the bearing groove structures of the thrust bearing only radially inward of the opening the recirculation channel are arranged. Radially outside the thrust bearing is the bearing gap by sealing means, for example a capillary seal, sealed.

At an arranged inside the bearing bush end of the shaft a stopper ring arranged as a safeguard against falling out of the shaft. The stopper ring may according to another embodiment the invention additionally fulfill sealing functions.

Of the Spindle motor is preferably for operating speeds of less than 4200 rpm. In particular, he is the drive a 2.5-inch hard disk drive. The hard disk drive preferably comprises at most two storage disks and a writing and reading device for writing and reading data on and off the storage disk. The storage disk is from the spindle motor driven.

The Invention will become more apparent hereinafter with reference to the drawing figures explained. This results from the drawings and their Description of further features and advantages of the invention.

Brief description of the drawings

1 : shows a section through a first embodiment of a spindle motor according to the invention

2 : shows a plan view of the end face of the bearing bush and a bearing surface of the fluid dynamic thrust bearing

3 shows a plan view of the end face of the bearing bush and a bearing surface of the fluid dynamic thrust bearing according to a second embodiment of the invention.

4 : shows a section through a second embodiment of a spindle motor according to the invention

Description of preferred Embodiments of the invention

1 shows a section through a spindle motor according to the invention with a fluid dynamic bearing system. The storage system includes a fixed bushing 10 having a central bore. Into the bore of the bearing bush 10 is a wave 12 used, whose diameter is slightly smaller than the diameter of the bore. Between the surfaces of the bearing bush 10 and the wave 12 there remains a bearing gap 16 which is filled with a bearing fluid, for example bearing oil. There are two fluid dynamic radial bearings 18 . 22 formed, by means of which the shaft 12 around a rotation axis 14 rotatable in the bore of the bearing bush 10 is stored. The radial bearings are through bearing groove structures 20 . 24 characterized in that generate a pumping action on the bearing fluid upon rotation of the bearing components and make the radial bearing viable. The radial bearings 18 . 22 are through a separator 34 separated from each other. In the area of the separator, the gap width of the bearing gap is increased.

A free end of the shaft is with a rotor component 26 connected. 1 shows a storage system in the so-called top thrust design, ie it is a single fluid dynamic thrust bearing 28 existing, which between the upper end of the bearing bush 10 and a lower surface of the rotor structure part 26 is trained. One of the bearing surfaces of the thrust bearing 28 , preferably the surface of the bearing bush 10 , is with bearing groove structures 30 ( 2 ) provided during rotation of the shaft 12 a pumping action on the between the rotor component 26 and end face of the bearing bush 10 exert bearing fluid, so that the thrust bearing 28 becomes sustainable. The bearing gap 16 extends axially along the shaft 10 and the radial bearings 18 . 22 and then further radially along the end face of the bearing bush 10 and the thrust bearing 28 ,

The bearing is at the lower end of the shaft through a cover plate 42 closed in the recess in the bearing bush 10 the lower end of the shaft is arranged opposite. At the bottom of the shaft 12 is a one-piece with the shaft or a separately formed stopper ring 38 arranged, which has an enlarged outer diameter compared to the diameter of the shaft. The stopper ring 38 prevents the shaft from falling out 12 from the bushing 10 , Between a gap 36 on the outer edge of the thrust bearing 28 and the gap area adjacent to the outer diameter of the stopper ring 38 is a recirculation channel 32 intended. The recirculation channel 32 connects remote areas of the storage gap 16 together. The recirculation channel 32 runs from one to the stopper ring 38 adjacent area of the storage gap 16 up to one in the area of the thrust bearing 28 lying section of the storage gap. Due to the bearing groove structures of the axial and radial bearings, a predominantly in the direction of the stop locking 38 directed pumping action on the bearing fluid exerted. The bearing fluid circulates in the bearing gap 16 starting from the axial bearing 28 over the radial bearings 18 and 22 down and from there via the recirculation channel 32 back to the outside of the thrust bearing 28 where it is due to the radially inward pumping action of the thrust bearing 28 again in the direction of the radial bearings 18 . 22 is pumped.

At the outer diameter of the thrust bearing 28 the storage gap goes 16 in a sealing gap over, which now extends beyond the outer circumference of the bearing bush 10 continues and conically outward in the form of a conical capillary seal 40 extended.

The bearing bush 10 is in a base plate 46 which also includes an annular stator assembly 48 wearing. The stator arrangement 48 is surrounded by a rotor magnet 50 , which on the rotor component 26 is attached. The rotor magnet 50 is axially offset by an amount d to the stator assembly 48 on the rotor component 26 attached. This is the magnetic center of the rotor magnet 50 Located slightly above the center of the stator core, resulting in a down to the base plate 46 directed magnetic force F _M results, which by the thrust bearing 28 counteracts generated force.

In addition to the magnetic force F _M, the weight F _L acts on the rotor. Depending on the position of the spindle motor in the room this changes according to their direction. A hydraulic force F _{H is} generated by the hydrodynamic thrust bearing, which acts on the rotor opposite to the direction of the magnetic force F _M during rotation of the rotor and thus ensures that the rotor hovers a few micrometers above the bearing bushing. In this case, the hydraulic force F _H must always be greater than the sum of the forces F _M and F _L , so that the following applies: F _H ≥ F _M + F _L. When compared to the prior art reduced speeds of the engine, the hydraulic force F _H decreases in terms of amount accordingly. Therefore, the oppositely acting force F _{M can} also be made smaller in size accordingly.

2 shows a plan view of the end face of the bearing bush 10 , which is a bearing surface of the thrust bearing 28 formed. The thrust bearing 28 is by spiral groove-shaped bearing structures 30 characterized, extending from the bearing bore of the bearing bush radially outward. Since in spindle motors with at most two storage disks, the axial loads are relatively small, thus the weight F _{L is} lower and the required hydraulic axial force F _{H is} not so large, the surface of the thrust bearing 28 compared to the entire face of the bearing bush 10 be kept relatively small. Outside the bearing groove structures 30 of the thrust bearing 28 has the bearing bush 10 step up and go over into a plane 36a , which together with the opposite rotor component 26 a gap 36 forms with increased gap width. This gap 36 goes over into the sealing gap 40 ( 1 ). In a spindle motor for driving 2.5-inch hard disk drives, the diameter of the bearing bore or the diameter of the shaft is about 2.5 millimeters. The outer diameter of the bearing bush or the rotor component 26 arranged bearing surface of the thrust bearing 28 is less than 4.9 millimeters. By contrast, the overall diameter of the bearing bush is approximately 6.43 millimeters.

The recirculation channel 32 preferably opens radially outside of the thrust bearing 28 in the area of the area 36a So in the gap 36 ,

3 shows a plan view of the bushing 10 according to another embodiment of the invention. In this case, the bearing groove structures extend 28 of the thrust bearing 30 starting from the bearing bore to the outer edge of the bearing bush. The recirculation channel opens inside the bearing groove structures 28 of the thrust bearing 30 ,

The 4 shows a second embodiment ei nes spindle motor with a fixed shaft according to the invention. The spindle motor comprises a base plate 146 having a substantially central cylindrical opening in which a first bearing member 113 is included. The first bearing component 113 is approximately pot-shaped and comprises a central opening, in which a shaft 112 is attached. At the free end of the fixed shaft 112 is a second bearing component 138 arranged, preferably annular and integral with the shaft 112 is formed and serves as a stopper ring, among other things. The named components 146 . 112 . 113 and 138 form the fixed component of the spindle motor. The bearing comprises a bearing bush 110 in one by the shaft 112 and the two bearing components 113 . 138 formed intermediate space is rotatably arranged relative to these components. The upper bearing component 138 is in an annular recess of the bearing bush 110 arranged. Adjacent surfaces of the shaft 112 , the bearing bush 110 and the bearing components 113 . 138 are by a bearing gap open on both sides 116 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 146 arranged stator arrangement 148 and an annular rotor magnet surrounding the stator assembly at a distance 150 at an inner circumferential surface of a rotor component 126 is arranged. The rotor component 126 is on the bearing bush 110 attached. In principle, it is also possible, the rotor component 126 and the bearing bush 110 to train in one piece.

The bearing bush 110 has a cylindrical bore on the inner circumference of two cylindrical radial bearing surfaces are formed, which by an intermediate circumferential Separator groove 134 are separated. These storage areas enclose the standing wave 112 at a distance of a few microns to form an axially extending portion of the bearing gap 116 and are with suitable bearing groove structures 120 . 124 provided so that they match the respective opposite bearing surfaces of the shaft 112 two fluid dynamic radial bearings 118 and 122 form.

To the lower radial bearing 122 closes a radially extending portion of the bearing gap 116 on, by radially extending bearing surfaces of the bearing bush 110 and corresponding opposite bearing surfaces of the first bearing component 113 is formed. These bearing surfaces form a fluid dynamic thrust bearing 128 in the form of an axis of rotation 114 vertical circular ring (cf. 2 and 3 ). The fluid dynamic thrust bearing 128 is in a known manner by, for example, spiral bearing groove structures 130 marked either on the front side of the bearing bush 110 , the first bearing component 113 or both parts can be attached.

The rotor magnet 150 is axially offset by an amount d to the stator assembly 148 on the rotor component 126 attached. This is the magnetic center of the rotor magnet 150 Located slightly above the center of the stator core, resulting in a down to the base plate 146 directed magnetic force F _M results, which in the position shown in space together with the weight F _{L of} the rotor through the thrust bearing 128 counteracts generated hydraulic force F _H.

At the radial portion of the bearing gap 116 in the area of the thrust bearing 128 closes a proportionally filled with bearing fluid capillary seal 140 on, by opposing surfaces of the bearing bush 110 and the first bearing component 113 is formed and the end of the fluid bearing system seals on this side. In addition to the function as a capillary seal, the sealing gap is used 140 as a fluid reservoir and provides the required for the life of the storage system fluid amount.

On the other side of the fluid bearing system is the bearing bush 110 following the upper radial bearing 118 designed so that it forms a radial extending surface, which with a corresponding opposite surface of the second bearing component 138 forms a radial gap. At the radial gap, an axially extending sealing gap closes 141 which terminates the fluid bearing system at this end. The sealing gap 141 preferably comprises a pumping seal and expands at the outer end with preferably conical cross-section. The sealing gap 141 is made by opposing surfaces of the bearing bush 110 and the bearing component 138 limited and can by an annular cover 142 be covered. The cover 142 is at one stage of the bearing bush 110 attached.

In order to ensure a continuous flushing of the storage system with bearing fluid, in a known manner, a recirculation channel 132 intended. The recirculation channel 132 is inventively as axially or slightly obliquely extending channel in the bearing bush 110 formed, preferably at an acute angle with respect to the axis of rotation 114 of the warehouse is arranged. The recirculation channel 132 connects the two radial sections of the bearing gap 116 between the bearing areas and the sealing areas directly to each other and preferably ends in the radially outer portion of the thrust bearing, in which the axial gap 136 larger than the portion of the radial bearing gap which is located closer to the shaft. Due to the directed pumping action of the bearing groove structures of the thrust bearing 128 and the radial bearing 118 . 122 results in the bearing gap 116 preferably a flow of the bearing fluid in the direction of the upper sealing gap 141 , In addition, the bearing fluid in the recirculation channel 132 due to the effect of centrifugal force in the inclined channel downwards in the direction of the thrust bearing 128 promoted, so that sets a stable fluid circuit.

LIST OF REFERENCE NUMBERS

10 110

bearing bush

12 112

wave

113

bearing component

14 114

axis of rotation

16 116

bearing gap

18 118

radial bearings

20 120

Bearing groove structures

22 122

radial bearings

24 124

Bearing groove structures

26 126

rotor component

28 128

thrust

30 130

Bearing groove structures

32 132

recirculation

34 134

separator

36 136

gap

36a

area

38 138

Stopper ring bearing component

40 140

capillary

141

seal gap

42 142

cover, cover

44

disk

46 146

baseplate

48 148

stator

50, 150

rotor magnet

d

axial offset

FM

magnetic force

FL

weight force

FH

hydraulic force

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102007039231 A1 [0002]

Claims (19)

Spindle motor with at least one fixed motor component and at least one by means of a fluid dynamic bearing system about a rotation axis ( 14 ; 114 ) rotatably mounted engine component, wherein the storage system at least one fluid dynamic radial bearing ( 18 . 22 ; 118 . 122 ) and a single fluid dynamic thrust bearing ( 28 ; 128 ), whereby during operation of the motor, an axial hydraulic force F _{H is} generated and wherein means for generating a magnetic force component F _M for the thrust bearing ( 28 ; 128 ) are driven, and the rotatably mounted engine component is driven by an electromagnetic drive system, wherein the forces F _H and F _{M are} oppositely directed, characterized in that the means for generating a magnetic bias for the thrust bearing ( 28 ; 128 ) consist exclusively of components of the electromagnetic drive system. Spindle motor according to claim 1, characterized in that the electromagnetic drive system comprises a stator arrangement ( 48 ; 148 ) and a rotor magnet ( 50 ; 150 ), wherein the magnetic center of the rotor magnet ( 50 ; 150 ) is offset by an amount d with respect to the magnetic center of the stator assembly, whereby the axial magnetic force F _{M is} generated. Spindle motor according to claim 1 or 2, characterized in that the fixed motor component comprises a base plate ( 46 ; 146 ), mounted in the base plate bearing bush ( 10 ) and the stator arrangement ( 48 ) of the electromagnetic drive system. Spindle motor according to one of claims 1 to 3, characterized in that the rotatably mounted engine component in a bearing bore of the bearing bush ( 10 ) recorded wave ( 12 ), a rotor component connected to the shaft ( 26 ) and the rotor magnet fixed to the rotor member ( 50 ) having. Spindle motor according to claim 1 or 2, characterized in that the fixed motor component comprises a base plate ( 46 ; 146 ), a fixed in the base plate first bearing component ( 113 ), a fixed shaft ( 112 ), a second bearing component ( 138 ) and the stator arrangement ( 148 ) of the electromagnetic drive system. Spindle motor according to one of claims 1, 2 or 5, characterized in that the rotatably mounted engine component one around the shaft ( 112 ) rotatably mounted bearing bush ( 110 ), a rotor component connected to the shaft ( 126 ) and the rotor magnet fixed to the rotor member ( 150 ) having. Spindle motor according to one of claims 1 to 6, characterized in that the radial bearing ( 18 . 22 ; 118 . 122 ) and the thrust bearing ( 28 ; 128 ) Have bearing surfaces which are filled by a bearing gap filled with a bearing fluid ( 16 ; 116 ) are separated from each other. Spindle motor according to one of claims 1 to 7, characterized in that it has two spaced-apart radial bearings ( 18 . 22 ; 118 . 122 ), which by mutually associated bearing surfaces of the bearing bush ( 10 ; 110 ) and the wave ( 12 ; 112 ) and by Lagerrillenstrukturen ( 20 . 24 ; 120 . 124 ) Marked are. Spindle motor according to one of claims 1 to 8, characterized in that the thrust bearing ( 28 ) by mutually associated bearing surfaces of the bearing bush ( 10 ) and the rotor component ( 26 ) and by Lagerrillenstrukturen ( 30 ). Spindle motor according to one of claims 1 to 8, characterized in that the thrust bearing ( 128 ) by mutually associated bearing surfaces of the bearing bush ( 110 ) and the first bearing component ( 113 ) and by Lagerrillenstrukturen ( 130 ) Spindle motor according to one of claims 1 to 10, characterized in that in the bearing bush ( 10 ; 110 ) a recirculation channel filled with bearing fluid ( 32 ; 132 ), the portions of the storage gap ( 16 ; 116 ) connects to each other Spindle motor according to one of claims 1 to 11, characterized in that an opening of the recirculation channel ( 32 ; 132 ) in the area of the thrust bearing ( 28 ; 128 ) in the bearing gap ( 16 ; 116 ), said opening of the recirculation channel ( 32 ; 132 ) by bearing groove structures ( 30 ; 130 ) of the thrust bearing ( 128 ) is not covered. Spindle motor according to one of claims 1 to 12, characterized in that the bearing groove structures ( 30 ; 130 ) of the thrust bearing ( 28 ; 128 ) only radially within the opening of the recirculation channel ( 32 ; 132 ) are arranged. Spindle motor according to one of claims 1 to 13, characterized in that an open end of the bearing gap ( 16 ; 116 ) by sealant ( 40 ; 140 ; 141 ) are sealed. Spindle motor according to one of claims 1 to 14, characterized in that on one inside the bearing bush ( 10 ; 110 ) arranged end of the shaft ( 12 ; 112 ) one Stopper ring ( 38 ; 138 ) is arranged. Spindle motor according to one of claims 1 to 15, characterized in that the operating speed is smaller as 4200 rpm. is. Spindle motor according to one of claims 1 to 15, characterized in that it is in a 2.5-inch hard disk drives is installed. Spindle motor according to claim 1 to 17, characterized in that for hydraulic force F _H and for the magnetic force F _M the inequality F _H ≥ F _M + F _L applies, where F _L denotes the weight of the rotor. Hard disk drive with a form factor of 2.5 inches and a spindle motor according to one of claims 1 to 18 for driving at most two storage disks ( 44 ), and a writing and reading device for writing and reading data to and from the storage disk.

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