Low-profile spindle motor

Abstract

Low-profile spindle motor, which includes: a stationary motor component, comprising a base plate (10; 110), a shaft (12; 112) and an annular stopper component (18; 118) arranged at a free end of the shaft, a rotatable motor component (14; 114), a fluid dynamic bearing system for the rotary mounting of the rotatable motor component (14; 114) relative to the stationary motor component, comprising an upper fluid dynamic radial bearing (22; 122) and a lower fluid dynamic radial bearing (24; 124), wherein the upper and the lower radial bearings (22, 24; 122, 124) each have bearing groove structures (22a, 24a; 122a, 124a), and an electromagnetic drive system (42, 44; 142, 144) for driving the rotatable motor component (14; 114) about a rotational axis (40; 140), wherein the ratio between the height a of the spindle motor, defined by the distance between the underside of the base plate (10; 110) and the upper end face of the stopper component (18; 118), and the bearing span b, defined by the distance between the lower edge of the lower radial bearing (24; 124) and the upper edge of the upper radial bearing (22;122) greater than or equal to 1.53 and less than or equal to 1.66, characterized in that its height a is between 5 mm and 7 mm.;

Description

Field of invention

[0001] The invention relates to a low-profile spindle motor, in particular a spindle motor with a fluid dynamic bearing system, such as can be used to drive a hard disk drive (HDD). State of the art

[0002] Spindle motors, as used to drive modern hard disk drives as electronic storage media, are miniature motors that are rotatably mounted using a fluid dynamic bearing system.

[0003] Such a spindle motor comprises a stationary motor component and a rotatable motor component, which is rotatably mounted relative to the stationary motor component about a rotational axis by means of a fluid dynamic bearing system. The rotatable motor component is driven in a known manner by an electromagnetic drive system consisting of a stator with coil windings and a permanent magnet rotor. Such a spindle motor is typically mounted on a base plate, which simultaneously serves as a lower housing component and can be closed by means of a housing cover.

[0004] Typically, corresponding components of the stationary and rotating motor parts are simultaneously designed as bearing components, featuring corresponding bearing surfaces separated by a bearing gap filled with a bearing fluid. Both fluid-dynamic radial bearings and at least one fluid-dynamic axial bearing are provided, which, in a known manner, have bearing groove structures associated with the bearing surfaces. During relative movement of the bearing components, these groove structures exert a pumping effect on the bearing fluid located in the bearing gap. This pumping action generates a hydrodynamic pressure within the bearing gap, which separates the bearing surfaces almost frictionlessly during operation, thus enabling the bearings to bear loads.

[0005] There are two basic types of spindle motors: spindle motors with a fixed shaft and spindle motors with a rotating shaft.

[0006] DE 10 2008 052 469 A1 discloses a spindle motor with a stationary shaft, wherein the spindle motor has a base plate in which a first bearing component, approximately U-shaped in cross-section, is received. A shaft is fixed in a central opening of this U-shaped bearing component. A so-called stopper component, which is integrally formed with the shaft, is arranged at the free end of the shaft. A rotor component of the spindle motor rotates in the space between the bearing component, the shaft, and the stopper component. This rotor component is separated from the stationary motor components, i.e., the bearing component, the shaft, and the stopper component, by a bearing gap. The bearing gap is filled with a bearing fluid, and corresponding fluid-dynamic radial and axial bearings are arranged along this bearing gap. The bearing gap has two open ends, each sealed by sealing arrangements, preferably capillary sealing arrangements.At its upper end, the shaft has a threaded hole through which it is attached to a housing cover of the spindle motor or hard disk drive by means of an associated screw. The rotor component is driven by an electromagnetic drive system, which has a stator assembly located on the base plate and a rotor magnet attached opposite the stator assembly to an inner circumference of the rotor component.

[0007] Spindle motors of known design for driving 2.5-inch hard disk drives typically have a height of about 7 to 15 millimeters. Of this, approximately 4 to 8 mm is accounted for by the fluid dynamic bearing system, specifically the axially extending section of the bearing gap along which the fluid dynamic radial bearings are arranged. About two millimeters of height are used for securing the shaft in the bearing component, and a further 1.5 millimeters is accounted for by the height of the stop component and its associated cover.

[0008] Mobile electronic devices, which typically use storage media such as laptops, notebooks, netbooks, notepads, tablet PCs, and other devices, are becoming increasingly smaller and thinner. This necessitates the development of correspondingly low-profile hard disk drives and spindle motors to accommodate these devices. Spindle motors must therefore keep pace with the development of mobile devices, with a future spindle motor height of approximately 5 mm to 7 mm being targeted. To achieve this, significant design modifications are required compared to the conventional design described above. On the one hand, the radial bearing span of the radial bearings should be kept as small as possible to avoid compromising stability and bearing stiffness. On the other hand, the clamping of the shaft within the bearing component must also be optimized.The height of the stopper component must not be too low, otherwise the necessary connecting forces between the components cannot be achieved. Furthermore, the capillary sealing gaps require sufficient space to ensure adequate sealing even under shock loads.

[0009] A spindle motor with the features of the preamble of claim 1 is disclosed in US 5 427 456 A and DE 10 2008 033 167 A1.

[0010] DE 695 13 473 T2 discloses a spindle motor with a ratio of installation height to bearing span of approximately 1.40.

[0011] DE 10 2009 022 997 A1 discloses a spindle motor with a ratio of shaft length to axial distance of radial bearings of less than or equal to 2.1. Further prior art, in particular concerning the features of the dependent claims, is disclosed in EP 1 750 352 A2, DE 10 2008 063 092 A1, DE 10 2007 058 151 A1 and US 2006 / 0 031 864 A1. Disclosure of the invention

[0012] The object of the invention is to design a spindle motor of the type mentioned above with a low overall height, without impairing bearing stability and functionality.

[0013] This problem is solved according to the invention by a spindle motor with the features of claim 1.

[0014] Preferred embodiments of the invention and further advantageous features are specified in the dependent patent claims.

[0015] The spindle motor comprises a stationary motor component with a shaft and an annular stop component arranged at a free end of the shaft, as well as a rotatable motor component which is rotatably mounted relative to the stationary motor component by means of a fluid dynamic bearing system. The fluid dynamic bearing system comprises an upper fluid dynamic radial bearing and a lower fluid dynamic radial bearing, the upper and lower radial bearings each having bearing groove structures. The rotatable motor component is driven by an electromagnetic drive system.

[0016] Here, the ratio between the height a of the spindle motor, defined by the distance between the underside of the base plate and the upper end face of the stopper component, and the bearing span b, defined by the distance between the lower edge of the lower radial bearing and the upper edge of the upper radial bearing, is greater than or equal to 1.53 and less than or equal to 1.66.

[0017] The invention is characterized in that the height a of the spindle motor is between 5 mm and 7 mm.

[0018] In a preferred embodiment of the invention, the spindle motor comprises a housing cover which rests directly on an annular surface of the stopper component and is attached to the shaft by means of a screw which engages in a central threaded bore of the shaft.

[0019] The screw provides the stopper component with additional holding force for attachment to the shaft, since with a flat spindle motor, as designed here, only a relatively small axial joining length between shaft and stopper component is available, which alone would not provide sufficient strength.

[0020] The stop component has a central bore into which the shaft engages with its end, which has a reduced diameter facing the housing cover. Beyond the step on which the stop component rests, i.e., in the section of the shaft connected to the stop component, the shaft has a smaller outer diameter than in the remaining section along which the radial bearings are arranged. The step on the shaft forms a flat bearing surface for the stop component, allowing for more precise alignment of the stop component with the shaft. Ideally, the stop component must be positioned exactly perpendicular to the shaft's axis of rotation. This bearing surface, which also acts as a stop, facilitates easier and more precise axial positioning of the stop component on the shaft.

[0021] The section of the bore of the stopper component facing the housing cover, which is not penetrated by the shaft, is chamfered, i.e., the diameter of this section widens from the shaft to the upper end face of the stopper component.

[0022] In a preferred embodiment of the invention, the housing cover has at least one projection directed towards the stopper component, which engages in the widening area of ​​the central bore of the stopper component and secures the housing cover in its position on the stopper component. This projection can also be formed by deforming the housing cover by screwing the fastening screw into the shaft.

[0023] The shaft is held in a stationary bearing component, which in turn is attached to a base plate of the spindle motor. The stationary bearing component can be formed as a single unit with the shaft, but preferably it is designed as a separate component from the shaft.

[0024] The shaft has a T-shaped cross-section and has a corresponding flange at one end, which extends radially in relation to the axis of rotation of the spindle motor and forms an axial bearing surface of the fluid dynamic bearing system, with the stationary bearing component being materially bonded to the flange of the shaft.

[0025] The bearing gap formed between the bearing components of the fluid dynamic bearing system is sealed by at least one sealing gap partially filled with a bearing fluid, which is designed as a conical capillary seal, wherein a labyrinth seal or gap seal is arranged beyond the sealing gap, which is partially free of bearing fluid.

[0026] This labyrinth seal or gap seal provides additional protection against the escape of bearing fluid from the sealing gap and also prevents excessive evaporation of bearing fluid from the bearing. Preferably, additional gap seals or labyrinth seals are provided in the area of ​​both sealing gaps.

[0027] In a preferred embodiment of the invention, the rotatable motor component has a thread on its outer circumference for attaching a threaded fastening element. For example, if the spindle motor is used to drive a hard disk drive, storage disks can be attached to the rotatable motor component using this fastening element.

[0028] As described above, the stationary bearing component at the lower end of the shaft can be formed as a single unit with the shaft, thus eliminating the need for the previously common press-fit, adhesive bonding, or (laser) welding connection between the shaft and the stationary bearing component. However, a one-piece design of the shaft and bearing component makes machining the outer circumference of the shaft and the upper end face of the shaft flange more difficult. In particular, the bearing surfaces of the radial bearing and the bearing surfaces of an axial bearing must be machined very precisely and, if necessary, surface-treated, for example, coated with sliding- and / or wear-resistant layers such as diamond-like carbon (DLC) or nickel.

[0029] Therefore, it is preferred if the flange of the shaft and the bearing component are made from two separate parts and are only joined together after machining by means of a material-bonded connection, by means of (laser) welding and / or press connection and / or adhesive connection.

[0030] The flange of the shaft is preferably designed as a flat disc and comprises a bearing surface of the axial bearing, while the stationary bearing component forms a boundary surface of a sealing arrangement for the bearing gap.

[0031] The spindle motor of the design according to the invention is particularly suitable for driving a low-profile hard disk drive, which has at least one storage disk that is driven by the spindle motor. Hard disk drives, as is known, have a read / write device for writing and reading data to and from the storage disk. The housing cover of the spindle motor is preferably also the housing cover of the hard disk drive.

[0032] The invention is described in more detail below with reference to several exemplary embodiments and the drawings. Further features and advantages of the invention will become apparent from the drawings and the following description. Brief description of the drawings: Fig. Figure 1 shows a section through a spindle motor according to the invention in a first embodiment. Fig. Figure 2 shows a section through a spindle motor according to the invention in a second embodiment. Description of preferred embodiments of the invention

[0033] The Fig. 1 and Fig. Figure 2 shows two slightly different embodiments of a low-profile spindle motor and a fluid dynamic bearing system according to the invention. Such a spindle motor can be used to drive the storage platters of a hard disk drive.

[0034] The spindle motors according to the Fig. 1 and Fig. 2 are largely identical in their basic structure and differ mainly in their height and the shape of the sealing gap. Fig. Figure 1 shows a spindle motor with a height of approximately 7 mm, while the Fig. Figure 2 shows a spindle motor with a height of approximately 5 mm.

[0035] Based on Fig. Section 1 describes the basic structure of the spindle motor according to the invention. The spindle motor comprises a base plate 10, which has a substantially central cylindrical opening in which a stationary bearing component 16 is received. The stationary bearing component 16 has an approximately U-shaped cross-section and a central opening. The stationary bearing component 16 is arranged, for example, with a transition fit in the opening of the base plate 10 and is preferably additionally secured with adhesive. To prevent static charges on the storage plates 56, conductive adhesive is applied at least at one point along the circumference of the stationary bearing component 16 between the base plate 10 and the stationary bearing component 16.

[0036] A cylindrical shaft 12 is provided, which has a flange 12a at one end, so that the shaft 12 has an approximately T-shaped cross-section. The flange 12a of the shaft is arranged in the central opening of the stationary bearing component 16, with the outer circumference of the flange 12a abutting the inner circumference of the bearing component 16 and preferably being metallurgically bonded to it. This metallurgical bond can be a circumferential weld 13. The stationary bearing component 16 can also be formed integrally with the flange 12a of the shaft 12, as shown in the Fig. Figure 3 illustrates this. However, this makes machining the surfaces of the shaft and the flange 12a more difficult. Due to the two-part design of the flange 12a and the bearing component 16, the bearing surfaces located on the outer circumference of the shaft and on the upper end face of the flange 12a can be machined much more easily. The cylindrical part of the shaft 12 extends axially upwards from the radially oriented base surface of the flange 12a.

[0037] At the free end of the shaft 12, an annular stop component 18 is arranged, the diameter of which is significantly larger than the diameter of the shaft 12 and which is preferably attached to the shaft 12 by frictional or material bonding. In particular, the shaft 12 has a reduced diameter at its free end, forming a step 12b. The step 12b defines a stop for the stop component, against which the stop component 18 rests. This ensures that the stop component 18 is precisely positioned and aligned on the shaft and that a holding force in the axial downward direction is maintained. Furthermore, this step 12b defines an axial space on the shaft 12 for receiving a bearing bushing 14a. The shaft 12 with the flange 12a, together with the bearing component 16 and the stop component, forms a compact assembly. The entirety of the aforementioned components 10, 12, 12a, 16 and 18 forms the stationary bearing component of the spindle motor.

[0038] The spindle motor further comprises a rotor component 14, which includes a cylindrical bearing bushing 14a. The rotor component 14, more precisely the bearing bushing 14a of the rotor component 14, is rotatably arranged about an axis of rotation 40 in a space formed by the shaft 12, 12a and the two components 16, 18, relative to these components 12, 12a, 16, 18. The stop component 18 is arranged at least partially in an annular recess of the rotor component 14.

[0039] Adjacent surfaces of the shaft 12, 12a of the bearing bushing 14 and of the two components 16, 18 are separated from each other by a bearing gap 20 open on both sides, which is filled with a bearing fluid, for example a bearing oil.

[0040] The bearing bushing 14a, preferably formed in one piece and arranged on the rotor component 14, has a cylindrical bearing bore with two cylindrical radial bearing surfaces formed on its inner circumference. These surfaces are axially spaced apart from each other by a separator gap 26. The radial bearing surfaces surround the stationary shaft 12 at a distance of between 1.5 and 3.5 micrometers, forming an axially extending section of the bearing gap 20. Together with the opposing bearing surfaces of the shaft 12, they form two fluid-dynamic radial bearings 22 and 24. The bearing surfaces of the two radial bearings 22 and 24 are provided, for example, with sinusoidal or parabolic (herringbone) groove structures 22a and 24a. The upper radial bearing 22 is largely symmetrical, meaning that the portion of the groove structures 24 located above the apex is approximately the same length as the lower portion of the grooves.The pumping action of both parts of the radial bearing grooves 24 is directed towards the apex, i.e., towards the bearing center, thus enabling the radial bearing 22 to bear load. However, due to the symmetrical design of the radial bearing grooves 24 of the upper radial bearing 22, there is no defined pumping direction acting on the bearing fluid in the bearing gap 20. In contrast, the lower radial bearing 24 is asymmetrically designed in that the part of the bearing groove structures 24a located below the apex is longer than the upper part of the radial bearing grooves 24a. This results, on the one hand, in a pressure increase within the bearing fluid towards the apex of the radial bearing 24, which enables the radial bearing 24 to bear load. On the other hand, a defined pumping action is exerted on the bearing fluid in the bearing gap 20, which conveys the bearing fluid axially upwards towards the upper radial bearing 22.The separator gap 26 has a significantly larger gap width compared to the axial section of the bearing gap 20.

[0041] Below the lower radial bearing 24, the axially extending section of the bearing gap 20 transitions into a radially extending section along which a fluid-dynamic axial bearing 28 is arranged. The axial bearing 28 is formed by radially extending bearing surfaces on the end face of the bearing bushing 14a and correspondingly opposing bearing surfaces on the flange 12a of the shaft 12. The bearing surfaces of the axial bearing 28 are designed as circular rings perpendicular to the axis of rotation 40. The fluid-dynamic axial bearing 28 is characterized in a known manner by, for example, helical bearing groove structures, which can be provided either on the end face of the bearing bushing 14a, the flange 12a, or on both.

[0042] Preferably, the axial bearing surface is arranged only between the radially extending surface of the flange 12a and the opposite underside of the bearing bushing 14a. The adjacent and also radially extending surface of the stationary bearing component 16 is arranged approximately 10 to 100 micrometers lower than the radially extending surface of the flange 12a, resulting in a correspondingly larger gap between the radially extending surfaces of the bearing bushing 14a and the stationary bearing component 16 in the assembled state of the fluid dynamic bearing.

[0043] Advantageously, all the bearing groove structures required for the radial bearings 22, 24 and the axial bearing 28 are arranged on corresponding bearing surfaces of the bearing bushing 14a, which simplifies the manufacture of the bearing, in particular the high-precision bearing surfaces on the shaft 12 and the flange 12a. Preferably, the axial bearing grooves open radially outwards into an annular gap that has a larger gap width than the axial bearing gap. This annular gap begins approximately at the point where a recirculation channel 30, which is provided within the rotor component 14, opens into the radial extension of the axial bearing gap 28.

[0044] A first capillary sealing gap 34, partially filled with bearing fluid, adjoins the radial section of the bearing gap 20 in the area of ​​the axial bearing 28 or the annular gap. The sealing gap 34 is formed by opposing, essentially axially extending surfaces of the bearing bushing 14a and the bearing component 16 and seals the bearing gap 20 on this side. The sealing gap 34 comprises the short, radially extending section of the annular gap, which is wider than the bearing gap 20 and is located radially outside the axial bearing 28. The short, radially extending section of the sealing gap 34 transitions into a longer, conically widening, and almost axially extending section, which is bounded by an outer circumferential surface of the bearing bushing 14a and an inner circumferential surface of the bearing component 16.In addition to its function as a capillary seal, the sealing gap 34 serves as a fluid reservoir, providing the required amount of fluid for the service life of the bearing system. Furthermore, it can compensate for filling tolerances and any thermal expansion of the bearing fluid. The two surfaces of the bearing bushing 14a and the bearing component 16, which form the conical section of the sealing gap 34, can both be inclined inwards relative to the axis of rotation 40 towards the outer side of the bearing along the sealing gap. The angle of inclination is preferably between 0 and 5 degrees. The angle of inclination of the outer circumferential surface of the rotor component 14 is greater than the angle of inclination of the inner circumferential surface of the bearing component 16, resulting in a conical widening of the capillary seal. This causes the bearing fluid to be forced inwards towards the bearing gap 20 by centrifugal force when the bearing rotates.

[0045] On the other side of the bearing system, the rotor component 14 or the bearing bushing 14a, adjacent to the upper radial bearing 22, is designed such that it forms a radially extending surface which, together with a correspondingly opposing surface of the stopper component 18, forms a radial gap. Adjoining the radial gap is a second axially extending sealing gap 36, which is partially filled with bearing fluid and seals the bearing gap 20 at this end. The second sealing gap 36 is bounded by opposing surfaces of the rotor component 14 and the stopper component 18 and widens at its outer end, preferably with a conical cross-section. The outer circumferential surface of the stopper component 18 is slightly inclined inwards towards the axis of rotation 40 as it extends towards the outer edge of the bearing.The opposing inner circumferential surface of the rotor component 14 either runs parallel to the axis of rotation 40 or is also slightly inclined inwards, the angle of inclination being smaller than that of the outer circumferential surface of the stopper component 18, thus forming a conical capillary seal. The second sealing gap 36 can preferably be supplemented by a pump seal 38, which is arranged below the capillary seal. The pump seal 38 is preferably formed between the outer circumference of the stopper component 18 and the opposing surface of the rotor component 14. The pump seal 38 comprises groove structures 39, which are arranged on the surface of the stopper component 18 or, preferably, the rotor component 14. As the bearing rotates, the groove structures 39 of the pump seal 38 generate a pumping action on the bearing fluid located in the sealing gap 36.This pumping action is directed into the interior of the bearing gap, i.e., towards the radial bearing 22. The pump groove structures may extend partially into the lower region of the capillary seal. Preferably, however, the pump groove structures 39 do not extend into the radially extending gap formed between the underside of the stopper component 18 and the bearing bushing 14a.

[0046] The second sealing gap 36 is covered by an annularly profiled cover 32. The cover 32 is attached to an edge of the rotor component 14, for example, by gluing, with the cover 32 resting on a circumferential edge of the rotor component 14. An inner edge of the cover 32, together with the outer circumference of the stopper component 18, forms an air gap as a gap seal 54. This gap seal 54 increases the protection against the escape of bearing fluid from the sealing gap 36 and / or reduces the evaporation of the bearing fluid, thus increasing the service life of the fluid bearing.

[0047] At the axially outer end of the sealing gap 36, the sealing gap widens into a free space 50, which is preferably large enough to accommodate the entire volume of bearing fluid in the bearing. This free space 50 serves in particular for filling the bearing with bearing fluid. For this purpose, the bearing gap and the sealing gaps are preferably evacuated, and the total volume of bearing fluid is filled into the free space 50. The bearing gap is then vented again, which forces the volume of bearing fluid from the free space 50 into the bearing and the sealing gaps.

[0048] A recirculation channel 30 runs obliquely downwards from the gap between the end face of the rotor component 14 and an opposite end face of the stopper component 18 through the rotor component 14 and opens radially outside the axial bearing 28 into the radially extending section of the sealing gap 34 (annular gap).

[0049] The spindle motor has an electromagnetic drive system formed in a known manner by a stator assembly 42 arranged on the base plate 10 and an annular permanent magnet 44 concentrically surrounding the stator assembly at a distance and arranged on an inner circumferential surface of the rotor component 14. Thus, an external rotor motor is shown; however, an internal rotor motor can alternatively be used without restriction, in which the stator assembly is arranged radially outside the rotor magnet.

[0050] Since the spindle motor preferably has only a single fluid-dynamic axial bearing 28, which generates a force on the rotor component 14 in the direction of the stop component 18, a corresponding counterforce or preload force is necessary to keep the rotor component 14 axially in force equilibrium. For this purpose, the stator assembly 42 and the rotor magnet 44 are arranged axially offset from each other, such that the magnetic center of the rotor magnet 44 is located axially further away from the base plate 10 than the center of the stator assembly 42. This causes the motor's magnetic system to exert an axial force on the rotor component 14, which acts opposite to the bearing force of the axial bearing 28 during operation. Furthermore, alternatively or additionally to the offset of the drive system below the rotor magnet 44, a tension ring 46 made of ferromagnetic material can be provided and attached to the base plate.The pull ring 46 is magnetically attracted by the rotor magnet 44, so that an axial magnetic force acting on the rotor component 14 is generated, which counteracts the bearing force of the fluid dynamic axial bearing 28.

[0051] Previously it was known that the free end of the shaft 12 was firmly connected to a housing cover 48 of the spindle motor or the hard disk drive at the end where the stopper component 18 is located by means of a screw connection.

[0052] Preferably, the housing cover 48 is provided that it does not rest directly on the end face of the shaft 12, but only on an end face of the stopper component 18.

[0053] The stop component 18 is preferably pressed onto the shaft 12 until it rests against the step 12b of the shaft. The axial height of the stop component is dimensioned such that the end face of the stop component 18 projects beyond the end face of the shaft 12, thus preventing contact between the housing cover 48 and the end face of the shaft 12. The housing cover 48 is connected to the shaft by means of a screw that engages in a threaded bore in the shaft 12. This direct connection between the shaft 12 and the housing cover 48 additionally presses the stop component 18, located between the shaft 12 and the housing cover 48, onto the step 12b of the shaft and secures it in place. Thus, despite a comparatively short axial joining length, the stop component 18 remains firmly connected to the shaft 12 even in the event of a shock.

[0054] At the upper end of the first sealing gap 34, where the sealing gap 34 is widest, the gap between the stationary bearing component 16 and the outer circumference of the bearing bushing 14a narrows considerably again, forming a labyrinth seal 52. This labyrinth seal 52 prevents both the escape of bearing fluid from the sealing gap 34 and excessive evaporation of the bearing fluid from the area of ​​the sealing gap 34, thus increasing the service life of the fluid bearing. The labyrinth seal has, for example, a gap width of approximately 60 µm and a length of 1 mm.

[0055] The spindle motor can preferably be used to drive a hard disk drive, wherein one or more storage disks 56 can be mounted on the rotor component 14. The storage disks 56 are placed on an outer flange of the rotor component 14 and spaced apart by a spacer 58.

[0056] The storage plates are attached to the rotor component by means of a threaded ring 60, which is screwed onto a thread 62 on the outer circumference of the rotor component 14.

[0057] The bearing grooves of the fluid dynamic bearing system are preferably manufactured by means of electrochemical machining (ECM), wherein the separator gap 26 is mechanically (as in the Fig. 1) or by means of ECM (as in the Fig. 2) is machined.

[0058] The overall height a of the spindle motor is defined by the distance between the underside of the base plate 10 and the upper end face of the stopper component 18. The bearing span b is defined by the distance between the lower edge of the lower radial bearing 24 and the upper edge of the upper radial bearing 22. The ratio of the overall height a to the bearing span b is 1.53 for the spindle motor in the embodiment shown here.

[0059] Fig. Figure 2 shows a spindle motor, which in its basic design is similar to the spindle motor of Fig. 1 corresponds. Identical components are identified here with the same reference symbols as in Fig. 1 denotes, where each digit is preceded by a “1”, so that the “10” in Fig. 1 of the “110” in Fig. 2 corresponds. Furthermore, reference is made to the basic description of the spindle motor according to Fig. 1 referred.

[0060] The spindle motor of Fig. 2 is reduced in height to approximately 5 millimeters, and it is immediately noticeable that this reduces the distance between the two radial bearings 122 and 124, i.e., the axial length of the separator gap 126 is significantly shorter than in the spindle motor of Fig. 1.

[0061] The housing cover 148 also rests directly on the front face of the stopper component 118, but not on the front face of the shaft 112.

[0062] The housing cover 148 is directly connected to the shaft 112 by means of a threaded screw 164, the threaded screw 164 engaging in a threaded bore of the shaft 112.

[0063] A countersunk screw can preferably be used as the threaded screw 164, which, when screwed into the shaft 112, presses the (possibly previously formed) edges of the bore in the housing cover 148 into the chamfered bore of the stop component 118 and thus fixes the housing cover 148 immovably to the stop component.

[0064] For additional sealing of the first sealing gap 134, a labyrinth seal with axial extension between the bearing component 116 and the bearing bushing 114a cannot be used, as is shown in Fig. 1 is not used because the bearing's height is too low. Instead, a labyrinth seal 152 is proposed between the end face of the stationary bearing component 116 and a lower surface of the rotor component 114, or an axial gap 152 between an inner circumferential surface of the cylindrical shoulder of the base plate 110 and an outer circumferential surface of the rotor component 114. The upper gap or labyrinth seal 154 between the cover 132 and the stopper component 118 remains in place.

[0065] When using the spindle motor to drive a hard disk drive, a storage disk 156 can preferably be placed on the flange-like projection of the rotor component 114. The storage disk 156 is then screwed onto the thread 162 of the rotor component 114 by means of a threaded ring 160.

[0066] As an axial magnetic counter bearing for the fluid dynamic axial bearing 128, a tension ring 146 is used, which in this embodiment is designed as a profiled, flat sheet metal to save on overall height.

[0067] Overall, the stopper component 118 is also flatter than, for example, in the spindle motor of Fig. 1, so that the gap length of the upper sealing gap 136 in the axial direction becomes approximately smaller.

[0068] The ratio of the installation height a to the bearing span b is 1.66 for the spindle motor in the version shown here. List of reference symbols 10, 110 Base plate 12, 112 wave 12a, 112a flange 12b, 112b stage of the wave 13, 113 weld 14, 114 Rotor component 14a, 114a Bearing bushing 16,116 Bearing component 18, 118 Stopper component 20, 120 bearing gap 22, 122 radial bearings 22a, 122a Bearing groove structures 24, 124 radial bearings 24a, 124a Bearing groove structures 26, 126 separator gap 28, 128 axial bearings 30, 130 Recirculation channel 32, 132 Coverage 34, 134 Sealing gap 36, 136 Sealing gap 38, 138 Pump seal 39, 139 Pump groove structures 40, 140 axis of rotation 42, 142 Stator arrangement 44, 144 Rotor magnet 46, 146 Zugring 48, 148 Case cover 50, 150 free space 52, 152 Labyrinth seal 54, 154 Gap seal 56, 156 storage disk 58 spacers 60, 160 threaded ring 62, 162 threads 64, 164 Threaded screw 66, 166 conductive adhesive a building height b Bearing span

Claims

[1] Low-profile spindle motor comprising: a stationary motor component, comprising a base plate (10; 110), a shaft (12; 112) and an annular stopper component (18; 118) arranged at a free end of the shaft, a rotatable motor component (14; 114), a fluid dynamic bearing system for the rotary mounting of the rotatable motor component (14; 114) relative to the stationary motor component, comprising an upper fluid dynamic radial bearing (22; 122) and a lower fluid dynamic radial bearing (24; 124), wherein the upper and the lower radial bearings (22, 24; 122, 124) each have bearing groove structures (22a, 24a; 122a, 124a), and an electromagnetic drive system (42, 44; 142, 144) for driving the rotatable motor component (14; 114) about a rotational axis (40; 140), wherein the ratio between the height a of the spindle motor, defined by the distance between the underside of the base plate (10; 110) and the upper end face of the stopper component (18; 118), and the bearing span b, defined by the distance between the lower edge of the lower radial bearing (24; 124) and the upper edge of the upper radial bearing (22; 122) is greater than or equal to 1.53 and less than or equal to 1.66, characterized by , that its construction height a is between 5 mm and 7 mm. [2] Spindle motor according to claim 1, characterized by , that the shaft (12; 112) has a step on which the stopper component (18; 118) rests, wherein the end face of the stopper component (18; 118) projects axially beyond the end face of the shaft (12; 112), and a housing cover (48; 148) covering the spindle motor rests only on the end face of the stopper component (18; 118), but not on the end face of the shaft (12; 112). [3] Spindle motor according to claim 2, characterized by , that the housing cover (48; 148) is attached to the shaft (12; 112) by means of a screw (64; 164) which screw (64; 164) engages in a central threaded bore of the shaft (12; 112). [4] Spindle motor according to any one of claims 1 to 3, characterized by, that the stopper component (18; 118) has a central bore with a first section and a second section, wherein the shaft (12; 112) engages in the first section, and the diameter of the second section increases from the first section towards the upper end face of the stopper component (18; 118). [5] Spindle motor according to any one of claims 2 to 4, characterized by , that the housing cover (48; 148) has at least one projection directed towards the stopper component (18; 118) which engages in the central bore of the stopper component (18; 118). [6] Spindle motor according to any one of claims 1 to 5, characterized by , that the stopper component (18; 118) is connected to the shaft (12; 112) by means of an interference fit. [7] Spindle motor according to any one of claims 1 to 6, characterized by , that the shaft (12; 112) is held in a stationary bearing component (16; 116). [8] Spindle motor according to claim 7, characterized by, that the stationary bearing component is formed in one piece with the shaft (12; 112). [9] Spindle motor according to any one of claims 1 to 8, characterized by , that the shaft (12; 112) has a flange (12a; 112a) which extends radially with respect to the axis of rotation (40; 140) of the spindle motor and forms an axial bearing surface, and the stationary bearing component (16; 116) is materially bonded to the flange (12a; 112a) of the shaft (12; 112). [10] Spindle motor according to claim 9, characterized by , that the flange (12a; 112a) is formed in one piece with the shaft (12; 112). [11] Spindle motor according to any one of claims 1 to 10, characterized by, that a bearing gap (20; 120) of the fluid dynamic bearing system is sealed by at least one sealing gap (34, 36; 134, 136) partially filled with a bearing fluid, wherein a labyrinth seal (52; 54; 152; 154) is arranged beyond the sealing gap (34, 36; 134, 136) which is free of bearing fluid. [12] Spindle motor according to any one of claims 1 to 11, characterized by , that the rotatable motor component (14; 114) has a thread (62; 162) on an outer circumference for fastening a threaded fastening element (60; 160). [13] Low-profile hard disk drive with at least one storage disk (56; 156) which is driven by a spindle motor according to any one of claims 1 to 12, and which includes a read / write device for writing and reading data to and from the storage disk (56; 156).

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