Low-profile spindle motor

Abstract

Low-profile spindle motor, which includes: a stationary motor component with a shaft component (12, 16, 18), wherein the shaft component (12, 16, 18) has a cylindrical shaft (12) with two ends, wherein a bearing component (16) is arranged at one end of the shaft (12) and a stop component (18) is arranged at the other end of the shaft (12), a rotatable motor component (14), a fluid dynamic bearing system (22, 24, 28) for the rotary bearing of the rotatable motor component (14) relative to the stationary motor component, an electromagnetic drive system (42, 44) for driving the rotatable motor component (14) about a rotary axis (40), and a housing cover (46) for closing the spindle motor, wherein the shaft component (12, 16, 18) is connected to the housing cover (46) by means of a pin connection or a purely material-bonded connection, characterized in that the bearing component (516; 616) consists of a first part (516a; 616a) and a second part (516b, 616b), wherein the first part (516a; 616a) is formed integrally with the shaft (512; 612) and forms an axial bearing surface, and the second part (516b, 616b) is materially bonded to the first part (516a; 616a).

Description

Field of invention

[0001] The invention relates to a low-profile spindle motor according to the preamble of claim 1, in particular a spindle motor with a fluid dynamic bearing system, such as can be used to drive a hard disk drive. State of the art

[0002] Spindle motors, as used to drive modern hard disk drives, 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. Such a spindle motor is generally mounted on a base plate, which simultaneously serves as a lower housing component that can be closed by means of a housing cover.

[0004] As a rule, corresponding components of the stationary and the rotatable motor component are simultaneously designed as bearing components, which have mutually assigned bearing surfaces that are separated from each other by a bearing gap filled with a bearing fluid.

[0005] Both fluid dynamic radial bearings and fluid dynamic axial bearings are provided, which, in a known manner, feature bearing groove structures assigned to the bearing surfaces. These groove structures exert a pumping effect on the bearing fluid arranged in the bearing gap during relative movement of the bearing components. This pumping action of the bearing groove structures generates a hydrodynamic pressure within the bearing gap, which separates the bearing surfaces from each other with virtually no friction and enables the bearings to bear loads.

[0006] For radial bearings, for example, sinusoidal, parabolic or herringbone bearing groove structures are used, which are arranged on bearing surfaces of a stationary or rotatable bearing component that are arranged parallel to the axis of rotation of the bearing system.

[0007] For axial bearings, for example, spiral or herringbone bearing groove structures are used, which are arranged on bearing surfaces of a stationary or rotatable bearing component that are perpendicular to the axis of rotation.

[0008] There are two basic types of spindle motors: spindle motors with a fixed shaft and spindle motors with a rotating shaft.

[0009] DE 10 2008 031 618 A1 discloses a spindle motor with a stationary shaft, wherein the spindle motor has a base plate in which a first approximately U-shaped bearing component is received. A shaft is fixed in a central opening of this bearing component. A so-called stopper component 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.

[0010] 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.

[0011] The rotor component is driven by an electromagnetic drive system which has a stator arrangement located on the base plate and a rotor magnet which is attached opposite the stator arrangement on an inner circumference of the rotor component.

[0012] The width of the bearing gap between the stationary and moving bearing components is only a few micrometers in the area of ​​the radial bearings and about 10 to 30 micrometers in the area of ​​the axial bearing (during operation of the motor; when the motor is stationary, the axial bearing surfaces may lie on top of each other depending on the position of the bearing in space).

[0013] 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. A further two millimeters are used for securing the shaft in the bearing component, and the remaining approximately 1.5 millimeters comprise the height of the stop component and its associated cover.

[0014] Mobile devices, such as laptops, notebooks, notepads and other devices, are becoming increasingly smaller and flatter, so that corresponding hard disk drives and spindle motors with a correspondingly low profile must also be developed in order to be installed in the devices.

[0015] Spindle motors must therefore keep pace with the development of mobile devices. A spindle motor height of approximately 5 mm is targeted. To achieve this, significant design modifications are necessary compared to the conventional design described above. On the one hand, the radial bearing span of the radial bearings should not be reduced as much as possible, since this would significantly impair stability and bearing stiffness. On the other hand, the clamping of the shaft in the bearing component and the height of the stop component must not be too small, as this would prevent the necessary connecting forces between the components from being achieved. Furthermore, the capillary sealing gaps require sufficient installation space to ensure adequate sealing even under shock loads.

[0016] Furthermore, reducing the height of the stopper component makes it problematic or impossible to create the threaded hole for the shaft's fastening screw.

[0017] DE 10 2011 014 369 A1 discloses a spindle motor according to the preamble of claim 1. The spindle motor comprises a solid, pot-shaped bearing component with a relatively large height, which is mounted on the shaft.

[0018] US Patent 5,697,708 A also discloses a spindle motor with the essential features of the preamble of claim 1.

[0019] The JP 2001 - 305 468 A discloses a spindle motor with a shaft component and a pin connection between the shaft component and a housing cover.

[0020] DE 10 2005 036 396 A1 discloses a spindle motor with a pin connection between shaft and housing.

[0021] US 7 982 349 B2 reveals a pot-shaped bearing component that is mounted on the shaft. Disclosure of the invention

[0022] The object of the invention is to reduce the height of a spindle motor of the type mentioned above without compromising bearing stability and functionality.

[0023] This problem is solved according to the invention by a spindle motor with the features of claim 1.

[0024] Preferred embodiments of the invention and further advantageous features are specified in the dependent claims.

[0025] The low-profile spindle motor according to the invention comprises a stationary motor component with a shaft component, which has a cylindrical shaft with two ends, wherein a bearing component is arranged at one end of the shaft and a stop component is arranged at the other end of the shaft, a rotatable motor component, a fluid dynamic bearing system for rotating the rotatable motor component relative to the stationary motor component, an electromagnetic drive system for driving the rotatable motor component about an axis of rotation, and a housing cover for closing the spindle motor, wherein the shaft component is connected to the housing cover by means of a pin connection or a purely material-fit connection.

[0026] According to the invention, the bearing component consists of a first part and a second part, wherein the first part is formed integrally with the shaft and forms an axial bearing surface, and the second part is materially bonded to the first part.

[0027] A one-piece design of the shaft and the entire bearing assembly would make it difficult to machine the inner surfaces of the shaft assembly, which are bounded by the shaft and the bearing assembly. However, the bearing surfaces of the radial bearing and the bearing surfaces of an axial bearing, in particular, 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.

[0028] Therefore, according to the invention, it is preferred if the bearing component consists of a first and a second part, wherein the first part is formed integrally with the shaft and the second part is ring-shaped and is materially bonded to the first part.

[0029] The first part of the bearing component is preferably designed as a flat disk and, according to the invention, comprises a bearing surface of the axial bearing, while the second part of the bearing component forms a boundary surface of a sealing arrangement for the bearing gap. The two parts of the bearing component are preferably joined together by welding or bonding after the corresponding surfaces of the shaft and the bearing component, respectively, have been machined.

[0030] According to a first preferred embodiment of the invention, the shaft component has a pin at a free end which is aligned parallel to the axis of rotation and is received in an opening of the housing cover. The invention also includes the reverse of this arrangement, in which the housing cover has a pin on a surface facing the shaft component, which is received in an end-face opening of the shaft component.

[0031] The pin is preferably fixed to the shaft or to the housing cover.

[0032] However, a separate pin can also be provided. In this case, the shaft component and the housing cover have corresponding, mutually facing bores into which the separate pin engages and connects the two parts.

[0033] The pin is, for example, located at the free end of the shaft component and held in a blind hole or through-hole in the housing cover. It functions as a fastening screw, similar to those previously used in spindle motors of known design to secure the shaft. The pin is preferably aligned concentrically to the axis of rotation, but this is not mandatory. Furthermore, the pin can have a round or square cross-section. The pin can also be designed as an annular or polygonal ring. Multiple pins can also be used.

[0034] Generally, the shaft component does not need to have a discrete pin; rather, one end of the shaft component itself can be considered the pin, which is held in an opening in the housing cover. The opening in the housing cover must be adapted to the shape of the pin to ensure at least a positive-locking connection. The features mentioned above apply equally to the design of the spindle motor in which the pin is located on the housing cover and the opening for receiving the pin is located on the shaft component.

[0035] The shaft component not only comprises a cylindrical shaft with two ends, but also includes the described stopper component, which is attached to one end of the shaft, and a bearing component, which is attached to the other end of the shaft.

[0036] By eliminating the fastening screw and the threaded hole inside the shaft, the axial height of the stopper component can be reduced in particular, since the shaft without the threaded hole has better structural stiffness, which makes it possible to provide a shorter joining length for the preferably intended press connection between shaft and stopper component.

[0037] The lower height of the stopper component allows the spindle motor to be manufactured with a smaller overall height, without unnecessarily reducing the bearing span between the two radial bearings.

[0038] To securely connect the upper end of the shaft component to the housing cover, at least one positive-locking pin connection is to be used. In this design, the pin is inserted into the designated opening.

[0039] Preferably, however, a force-fit pin connection is to be used, for example in the form of a light press or fitting connection, or a material-fit pin connection, for example by fixing the pin in the opening by means of an adhesive connection.

[0040] In a preferred embodiment of the spindle motor, the stop component is ring-shaped and fitted onto the end of the shaft, preferably connected to the shaft by means of a friction-fit connection, such as a press fit, or a bonded connection, such as an adhesive bond. The shaft passes through the stop component. In this embodiment, the pin is arranged on an end face of the shaft facing the housing cover and secured in the opening of the housing cover. Alternatively, the pin is arranged on a side of the housing cover facing the shaft and secured in an opening of the shaft.

[0041] In this design of the spindle motor, the bearing component connected to the shaft is partially formed as a single unit with the shaft, thus eliminating the previously common press fit between the bearing component and the shaft. This allows the bearing component to be manufactured with a significantly lower profile than before, without compromising the stability of the connection between the shaft and the bearing component or requiring a reduction in the bearing clearance.

[0042] Through the measures described above, a spindle motor with a height of approximately 5 mm can be realized.

[0043] Preferably, various designs for the shape of the stopper component are provided, with a very flat design of the stopper component being preferred.

[0044] Due to the use of flat components, particularly a flat stopper component, special attention must be paid to the sealing arrangement formed between the surfaces of the stopper component and the rotor component of the spindle motor. A capillary seal is located between the axially extending outer circumference of the stopper component and the opposite inner circumference of the rotor component. Additionally, a pump seal is arranged between the capillary seal and the upper radial bearing. This pump seal either extends axially and is located between the outer circumference of the stopper component and the inner circumference of the rotor component, or it extends radially and is located between the underside of the stopper component and the opposite upper side of the rotor component. This pump seal has spiral grooves and, in the case of the radial orientation, can act as a (second) axial bearing.

[0045] In another embodiment of the spindle motor, the stopper component is designed as a type of cap and has a central opening in the form of a blind bore on one end face facing the shaft. The associated shaft has a pin on one end face facing the stopper component, which engages in the opening of the stopper component and is connected to the stopper component by means of a force-fit and / or material-fit connection, for example, a press fit and / or adhesive bond.

[0046] This design of the stopper component or the pin connection between the stopper component and the shaft allows for a very flat stopper component and at the same time a very strong connection, so that the overall height of the spindle motor can be reduced accordingly.

[0047] In the described embodiment, the pin for connecting the shaft component to the housing cover is arranged on the end face of the stop component facing the housing cover (cover plate). Alternatively, the pin for connecting the shaft component to the housing cover can be arranged on the housing cover and engage in a corresponding bore located on the end face of the stop component facing the housing cover.

[0048] In a modified embodiment of the spindle motor, the stopper component is also designed in the form of a cap and has a central pin on one end face associated with the shaft.

[0049] The associated shaft has an opening, for example a blind hole, on its end face facing the stop component. The stop component's pin engages in this opening and is connected to the shaft by means of a force-fit and / or material-fit connection (for example, a press fit and / or adhesive bond). This pin connection is very stable and allows for a flat stop component and a low overall height of the spindle motor. In this spindle motor configuration, the pin connecting the shaft component to the housing cover is either located on the upper end face of the stop component and engages in an opening in the housing cover, or the pin is located on the housing cover and engages in an opening in the stop component.

[0050] In all the embodiments described above, the stopper component preferably rests against the housing cover or is received in a flat recess of the housing cover.

[0051] A pin connection between the shaft component and the housing cover is not required; instead, the shaft component can lie flat against the housing cover and be bonded to it using a material-fit connection. An adhesive bond is preferred in this case. However, a welded connection between the shaft component and the housing cover is also possible.

[0052] A cover is preferably arranged on the rotatable motor component, which covers an open end of the fluid dynamic bearing system, in particular a sealing arrangement of the fluid dynamic bearing system.

[0053] The cover surrounds the stopper component in a ring shape and is separated from the stopper component by an air gap.

[0054] The cover can have a cross-sectional shape approximately U-shaped or, preferably, a flat, annular disc. The flat disc has the advantage of being easier to attach to the rotor component, eliminating the need for special recesses or other modifications to the rotor for securing the cover. This results in a reduction of approximately [amount missing] in the overall height of the spindle motor.

[0055] Preferably the shaft has a step on which the stopper component rests, i.e., in the section of the shaft which is connected to the stopper component, the shaft has a smaller outer diameter than in the remaining section along which the radial bearings are arranged.

[0056] The step on the shaft creates a flat contact 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.

[0057] This contact surface, which also acts as a stop, makes it easier and more accurate to position the stopper component on the shaft in the axial direction.

[0058] 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.

[0059] 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.

[0060] Brief description of the drawings: Fig. Figure 1 shows a section through a spindle motor in a first embodiment without a two-part bearing component. Fig. Figure 2 shows a section through a spindle motor in the first embodiment with a modified stopper component and without a two-part bearing component. Fig. Figure 3 shows a section through a spindle motor according to the first embodiment with a modified stopper component and without a two-part bearing component. Fig. Figure 4 shows a section through a spindle motor in a further embodiment without a two-part bearing component. Fig. Figure 5 shows a section through a spindle motor of further development with a modified form of the stopper component without a two-part bearing component. Fig. Figure 6 shows a section through the shaft and the two-part bearing component connected to the shaft in the embodiment according to the invention. Fig. Figure 7 shows a section through the shaft and the associated two-part bearing component in a further embodiment according to the invention. Fig. Figure 8 shows a section through the shaft and the associated bearing component in an unclaimed embodiment. Fig. Figure 9 shows a section through the shaft and the associated bearing component in an unclaimed embodiment. Fig. Figure 10 shows a modified and enlarged representation of the spindle motor of Fig. 4 in the area of ​​the stopper component. Fig. Figure 11 shows a modified and enlarged representation of the spindle motor of Fig. 5 in the area of ​​the stopper component. Fig. Figure 12 shows a further modified and enlarged representation of the spindle motor of Fig. 4 in the area of ​​the stopper component Fig. Figure 13 shows a further modified and enlarged representation of the spindle motor of Fig. 4 in the area of ​​the stopper component. Fig. Figure 14 shows a modified and enlarged representation of the spindle motor of Fig. 1 in the area of ​​the stopper component. Fig. Figure 15 shows a modified and enlarged representation of the spindle motor of Fig. 2 in the area of ​​the stopper component. Fig. Figure 16 shows a modified and enlarged representation of the spindle motor of Fig. 3 in the area of ​​the stopper component. Description of preferred embodiments of the invention

[0061] The Fig. Figures 1 to 5 show different configurations of a low-profile spindle motor and a fluid dynamic bearing system. Such a spindle motor can be used to drive the platters of a hard disk drive.

[0062] The spindle motors according to the Fig. Figures 1 to 5 are largely identical in their basic structure and differ mainly in the shape of the stop component and, in some cases, in the method of attaching the stop component to the shaft. Different covers for the bearing gap and the sealing area are also shown. For simplicity, the bearing component is depicted as a single-piece bearing component integrally connected to the shaft. This embodiment of the bearing component serves only to generally illustrate the structure and function of the spindle motor and is not claimed.

[0063] Based on Fig. Section 1 describes the basic structure of the spindle motor. 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 is approximately cup-shaped and is formed integrally with a shaft 12, which projects axially from a largely radially extending base surface of the bearing component 16 beyond the bearing component 16. An annular stop component 18 is arranged at the free end of the shaft 12, which is preferably frictionally or materially bonded to the shaft 12. The shaft 12, together with the bearing component 16 and the stop component, forms a compact assembly, which is hereinafter referred to as the shaft component.

[0064] The entirety of the aforementioned components 10, 12, 16 and 18 forms the stationary motor component of the spindle motor.

[0065] The spindle motor comprises a rotor component 14, which includes a cylindrical bearing bushing and a hub component integrally connected to the bearing bushing. The rotor component 14, more precisely the bearing bushing of the rotor component 14, is rotatably arranged about an axis of rotation 40 in a space formed by the shaft 12 and the two components 16, 18 relative to these components 12, 16, 18. The stop component 18 is at least partially arranged in an annular recess of the rotor component 14.

[0066] Adjacent surfaces of the shaft 12, the bearing bushing 14 and 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.

[0067] The bearing bushing arranged on the rotor component 14 has a cylindrical bearing bore, on the inner circumference of which two cylindrical radial bearing surfaces are formed, which are axially spaced apart from each other by a separator gap 26. The separator gap has a significantly larger gap spacing compared to the radial bearing gaps. The bearing surfaces enclose the stationary shaft 12 at a distance of a few micrometers, forming an axially extending section of the bearing gap 20, and together with opposing bearing surfaces of the shaft 12, they form two fluid-dynamic radial bearings 22, 24. The bearing surfaces of the two radial bearings 22, 24 are provided, for example, with sinusoidal or parabolic bearing groove structures 23, 25. The upper radial bearing 22 is largely symmetrical, meaning that the part of the bearing groove structures 24 located above the apex is approximately the same length as the lower part of the bearing 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 net pumping direction acting on the bearing fluid. In contrast, the lower radial bearing 24 is asymmetrically designed in that the part of the bearing groove structures 25 located below the apex is longer than the upper part of the radial bearing grooves 25. This results, on the one hand, in a pressure increase within the bearing fluid towards the apex of the radial bearing 22, thus enabling the radial bearing 22 to bear load. On the other hand, a net pumping action is exerted on the bearing fluid, which conveys the bearing fluid axially upwards towards the upper radial bearing 22.

[0068] 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 of the rotor component 14 and correspondingly opposing bearing surfaces of the bearing component 16. 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 29, which can be provided either on the end face of the rotor component 14, the stationary bearing component 16, or both parts.

[0069] Advantageously, all the bearing groove structures required for the radial bearings 22, 24 and the axial bearing 28 are arranged on bearing surfaces of the rotor component 14, which simplifies the manufacture of the bearing, particularly of the shaft 12 and the stationary bearing component 16. Preferably, the axial bearing grooves open radially outwards into an annular gap with a larger gap width than the axial bearing gap. This annular gap begins approximately at the point where a recirculation channel 30, provided within the rotor component 14, opens into the radial extension of the axial bearing gap 28.

[0070] Adjoining the radial section of the bearing gap 20 in the area of ​​the axial bearing 28 or the annular gap is a first capillary sealing gap 34, partially filled with bearing fluid. This gap is formed by opposing surfaces of the rotor component 14 and the bearing component 16 and seals the end of the bearing gap. 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. This short radially extending section of the sealing gap 34 transitions into a longer, conically widening, and nearly axially extending section, which is bounded by an outer circumferential surface of the rotor component 14 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 and provides the amount of fluid required for the service life of the bearing system.Furthermore, filling tolerances and any thermal expansion of the bearing fluid can be compensated for. The two surfaces forming the conical section of the sealing gap 34 on the rotor component 14 and the bearing component 16 can both be inclined inwards towards the outer edge of the bearing relative to the axis of rotation 40 along the course of the sealing gap. 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.

[0071] On the other side of the bearing system, the rotor component 14, adjacent to the upper radial bearing 22, is designed to form a radially extending surface that creates a radial gap with a correspondingly opposing surface of the stop component 18. 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 stop component 18 and widens at its outer end, preferably with a conical cross-section. The outer circumferential surface of the stop 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 grooves may extend partially into the lower region of 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 arranged on the surface of the stopper component 18 or 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 inwards within the bearing gap, i.e., in the direction of the radial bearing 22.

[0072] 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, resting on a flat, radially extending, end-face surface 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, acting as a gap seal. This increases the safety against the escape of bearing fluid from the sealing gap 36, reduces evaporation of the bearing fluid, and thus increases the service life of the fluid bearing.

[0073] At the axially outer end of the sealing gap 36, the sealing gap widens into a free space 52, which is preferably large enough to accommodate the entire volume of bearing fluid in the bearing. This free space serves in particular for filling the bearing with bearing fluid. For this purpose, the bearing gap and the sealing gap are preferably evacuated, and the total volume of bearing fluid is filled into the free space 52. The bearing gap is then vented again, which forces the volume of bearing fluid from the free space 52 into the bearing and the sealing gap.

[0074] 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).

[0075] 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.

[0076] 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 results in the motor's magnetic system exerting an axial force on the rotor component 14, which acts opposite to the bearing force of the axial bearing 28 during its operation.

[0077] Previously, it was known that the free end of the shaft in the area of ​​the stopper component was firmly connected to a housing cover of the spindle motor or the hard disk drive by means of a screw connection.

[0078] However, due to the flat design of the spindle motor, it is no longer possible to provide a corresponding threaded hole for the fastening screw in the shaft in order to screw it to the housing cover 46.

[0079] The shaft 12 is fastened to the housing cover 46 by means of a pin 48 arranged on the end face of the free end of the shaft 12. This pin 48 has only a short axial length and a significantly smaller diameter than the shaft 12. The pin is preferably arranged concentrically to the axis of rotation 40. The pin 48 can have a round or square cross-section.

[0080] The housing cover 46 has a bore 50 or recess associated with the pin 48.

[0081] When mounting the hard disk drive or spindle motor, the housing cover 46 is mounted in such a way that the pin 48 of the shaft 12 engages in the bore 50 of the housing cover 46 and secures the shaft 12 to the housing cover 46.

[0082] The connection between the pin 48 of the shaft 12 and the bore 50 of the housing cover 46 can, for example, simply be a positive-locking connection (plug connection). However, a force-locking connection, such as a press fit, or a material-locking connection, such as a weld or adhesive bond, is preferred.

[0083] The bore 50 in the housing cover 46 can be a through bore or merely a blind hole, as shown in the Fig. 1 is shown, depending on the available material thickness of the housing cover 46.

[0084] Fig. Figure 2 shows a spindle motor whose basic design is the spindle motor of Fig. 1 corresponds. Identical components are identified here with the same reference symbols as in Fig. 1. Reference is also made to the basic description of the spindle motor according to... Fig. 1 referred.

[0085] Unlike Fig. In particular, the stopper component 118 is designed as a relatively flat disc with a circumferential, downwardly angled edge around its outer circumference, directed towards the base plate. The stopper component 118 is mounted on a journal 112a of the shaft. A press fit, adhesive bond, or welded connection is proposed for the connection between the journal of the shaft and the stopper component. The stopper component 118 rests on a step of the shaft 112 and is thereby aligned perpendicularly and axially with the shaft 112.

[0086] The circumferential edge of the stopper component 118 is received in a recess 114a of the rotor component 114. A second sealing gap 36 is formed between the adjacent surfaces of the stopper component 118 and the rotor component 114. This gap extends radially outwards from the bearing gap 20, bends several times, and has a labyrinthine shape. The length of the sealing gap 36 is very large, thus achieving a good sealing effect. A pump seal 38 with pump groove structures 39 can be provided on an inner edge of the stopper component 118 and on an outer circumferential surface of the rotor component 114 in the area of ​​the recess 114a. A conical capillary seal is located in the area of ​​the transition from the bearing gap to the ambient atmosphere.

[0087] In this embodiment, the cover 132 of the sealing gap 36 is designed as a flat ring disc and requires little space, in particular a low height, and only a small recess in the rotor component 114 for fastening.

[0088] In this configuration, the bearing span between the two radial bearings 22, 24 can be made very large, since no additional axial height beyond the radial bearings is required for the formation of the sealing gap 36.

[0089] Due to its nested arrangement, the sealing gap 36 is partially at the same height as the upper radial bearing 22. This allows the axial section of the bearing gap 20, and thus also the radial bearing spacing, to be chosen to be very long and can be used for the arrangement of the radial bearings 22, 24, thereby increasing the bearing stiffness.

[0090] At Fig. 2. Furthermore, the advantage lies in the fact that the pump seal 38 is arranged on a relatively large diameter, which increases the overall pumping effect. The pump seal pumps the bearing fluid towards the inside of the bearing, i.e., towards the bearing gap.

[0091] The pin 112a of the shaft 112 is in turn provided with a pin 148 which engages in an associated through bore 150 of the housing cover 146 and is fastened there.

[0092] Fig. Figure 3 shows another modified design of a spindle motor based on the basic structure of Fig. 1. Identical components are identified here with the same reference symbols as in the Fig. 1 and Fig. 2. Reference is also made to the basic description of the spindle motor according to... Fig. 1 referred.

[0093] The stopper component 218 is ring-shaped and very flat and is attached to a pin 112a of the shaft 112, for example by welding, gluing or by means of a press connection.

[0094] The stopper component 218 lies in a corresponding recess of the rotor component 214 and forms a sealing gap on its outer circumference together with the rotor component 214, which may be supplemented by an additional pump seal 38 with pump groove structures 39.

[0095] The cover 232 is designed as a flat cover ring that covers the bearing at this end, with a recess 52 being formed under the cover 232, which serves for filling and as a reservoir of the bearing fluid.

[0096] The pin 148 for fastening the shaft 112 to the housing cover 46 is arranged on the shaft 112, in particular on the pin 112a of the shaft 112.

[0097] The pin 148 can be attached in the opening 50 of the housing cover 46 by a form-fit, force-fit or material-fit connection.

[0098] Fig. Figure 4 shows an embodiment of a spindle motor based on the basic structure of Fig. 1, in which the stopper component 318 is designed in the form of a cap and is placed on the shaft. The stopper component 318 has a flattened edge and a recess 318a directed towards the shaft and preferably centered on the axis of rotation 40.

[0099] The stopper component 318 is placed onto the shaft 312. For this purpose, the shaft 312 has a pin 312a that engages in the recess 318a of the stopper component 318. Preferably, the shaft 312 and the stopper component 318 are connected to each other in the area of ​​the pin 312a by means of a press fit and / or adhesive bond. In addition, the stopper component 318 rests on a step of the shaft 312 and is thus aligned with respect to the axis of rotation 40. The sealing gap 36 and the pump seal 38 are formed in the area of ​​the outer circumference of the stopper component 318.

[0100] In this embodiment, the stopper component 318 has a pin 348 on its end face concentric to the axis of rotation 40, wherein the pin 348, as already described several times, engages in an opening 50 of the housing cover 46 and is fixed there.

[0101] In particular, the stopper component 318 can, in all embodiments of the invention, lie directly against the housing cover 46 or also be arranged in a flat recess of the housing cover 46.

[0102] One advantage of the arrangement according to Fig. 4 is that no seal against leakage of the bearing fluid is required in the connection area between the shaft 312 and the stopper component 318, since the stopper component 318 completely covers the shaft 312 from above.

[0103] In the previous designs, it may be necessary to seal the connection area between the shaft and the stopper component to prevent oil from penetrating through the connection gap.

[0104] Fig. Figure 5 shows a design of a spindle motor similar to Fig. 4 or Fig. 1, where identical components are designated with the same reference numerals.

[0105] In this embodiment, the stop component 418 has a concentric pin 418a pointing downwards towards the shaft. This pin 418a is received in a blind bore 412b of the shaft. A press fit or adhesive bond can be provided between the shaft 412 and the stop component 418.

[0106] The stopper component 418 rests on an end face of the shaft 412 and is thereby aligned at a right angle with respect to the axis of rotation 40 of the motor.

[0107] A pin 448 for fastening the shaft component to the housing cover 46 is located on the stopper component 418.

[0108] In the Fig. Figures 1 to 5 each show a shaft component in which the bearing component is formed as a single piece with the shaft, resulting in a rigid structure. However, this one-piece design has the disadvantage that the surfaces in the annular space between the shaft and the edge of the bearing component are relatively difficult to machine. These surfaces, however, bear bearing surfaces and bearing groove structures that require very precise machining.

[0109] Furthermore, due to its design, a one-piece shaft and the bearing component mounted on the shaft cannot be manufactured from a hardenable material, as subsequent grinding of the shaft's outer diameter is not possible. A softer and more easily machinable material is not recommended due to the material combination and wear requirements.

[0110] Furthermore, due to the U-shape of the bearing component, no surface coating, such as a DLC coating, can be applied to the axial bearing surface of the bearing component.

[0111] In the Fig. 6 and Fig. Figure 7 shows a embodiment of the connection between the shaft and the bearing component arranged on the shaft according to the invention.

[0112] Fig. Figure 6 shows a section through a first embodiment according to the invention with a shaft 512, which is approximately T-shaped, wherein a first part 516a of the bearing component 516 is arranged as a flange in one piece at the end of the shaft 512. Thus, the surfaces located on the outer circumference of the shaft and on the upper end face of the component 516a can be machined without difficulty.

[0113] After surface processing, the bearing component 516 is completed by a second part 516b. The second part 516b is angled and ring-shaped, and is preferably bonded to the first part 516a, forming a circumferential edge that defines the boundary surface of the sealing gap. The bond can be, for example, a weld, a press fit, and / or an adhesive bond.

[0114] Preferably, the axial bearing surface is arranged only between the radially extending surface of the first part 516a of the bearing component 516 and the opposite underside of the rotor component. Furthermore, the radially extending surface of the second part 516b of the component 516 is arranged approximately 10 to 100 micrometers lower than the radially extending surface of the first part 516a of the component 516, resulting in a correspondingly larger gap in the assembled state of the fluid dynamic bearing. This area of ​​larger gap is part of the lower annular sealing gap into which the recirculation channel opens.

[0115] Fig. Figure 7 shows a further embodiment of the shaft 612 and a bearing component 616 attached to the shaft according to the invention. A first part 616a of the bearing component 616 is formed integrally with the shaft and extends from the shaft to the intended maximum diameter of the bearing component 616 in the form of a flat disk, which preferably has a small step 660 of between 10 and 100 micrometers in height in the radially extending surface in the transition area from the axial bearing gap to the sealing gap.

[0116] A ring-shaped element 616b is connected to the first component 616a after the surfaces of the shaft and the first component 616a have been machined, for example by welding or gluing.

[0117] Fig. Figure 8 shows an unclaimed embodiment of the connection between the shaft and the bearing component, in which the shaft 712 and the bearing component 716 are designed as two separate components.

[0118] The shaft 712 preferably has a journal 712a with a smaller diameter, which engages in an opening of the bearing component 716, wherein the components 712 and 716 are preferably joined together by a material bond, for example by welding or bonding. The bearing component 716 has an approximately cup-shaped cross-section and rests on a step of the shaft 712 and is thereby aligned relative to the shaft 712.

[0119] Fig. Figure 9 shows an unclaimed embodiment of the connection between the shaft and the bearing component, in which the shaft 812 has a substantially constant outer diameter, wherein the bearing component 816 is attached to one end of the shaft 812, for example by a press fit and / or welding or adhesive connection.

[0120] If the shaft 712 or 812 and the bearing component 716 or 816 are designed in two parts, it may be possible in these cases to design the shaft and the stopper component in one piece.

[0121] It will be in the Fig. 6 to 9 preferably proposes an arrangement of at least two parts for the shaft and the bearing component, wherein the parts are preferably joined by laser welding. The shaft can be hardened and ground before the final assembly of the bearing component.

[0122] This allows both the radial and axial bearing surfaces to be precisely machined and hardened. The second part of the bearing assembly can be made of the same material as the shaft and the first part of the bearing assembly, or of a different material, such as stainless steel, which is relatively easy to machine. This second part of the bearing assembly does not need to be hardened, as it only serves a sealing function and not a bearing function.

[0123] Fig. Figure 10 shows an enlarged section through a modified embodiment of a similar spindle motor, as described in Fig. 4 is shown. For Fig. 10. The general description of the spindle motor applies. Fig. 4. As in the example of Fig. 4 The stopper component 318' is mounted on the shaft 312. For this purpose, the shaft 312 has a pin 312a which engages in a recess 318a of the stopper component 318'. In contrast to Fig. 4 is used in the example of Fig. However, in Figure 10, a pin connection between the shaft component 318' and the housing cover 246 is omitted. Instead, the stop component 318', which forms part of the shaft component, has a flat upper end face. This flat upper end face rests directly against the housing cover 246. The stop component 318' and the housing cover 246 are connected to each other by means of a material bond, for example, an adhesive bond. Optionally, the housing cover 246 may have a shallow recess (not shown in the drawing) into which the end face of the stop component 318' engages.

[0124] Fig. Figure 11 shows an enlarged section through a modified embodiment of a similar spindle motor, as described in Fig. 5 is shown. For Fig. 11. The general description of the spindle motor applies. Fig. 5. As in the example of Fig. 5 The stopper component 418' is mounted on the shaft 412. The stopper component 418' has a pin 418a pointing downwards towards the shaft 412.

[0125] This pin 418a is received in a blind bore 412b of the shaft 412. In contrast to Fig. 5 is used in the example of Fig. Figure 11 omits a pin connection between the shaft component 418' and the housing cover 246. Instead, the stop component 418', which forms part of the shaft component, has a flat upper end face. This flat upper end face rests directly against the housing cover 246. The stop component 418' and the housing cover 246 are connected to each other by means of a material-bonded connection, for example, an adhesive bond. Optionally, the housing cover 246 may have a shallow recess (not shown in the drawing) into which the end face of the stop component 418' engages.

[0126] Fig. Figure 12 shows an enlarged section through another modified embodiment of a spindle motor similar to that in Fig. 4 is shown. For Fig. 12. The general description of the spindle motor applies. Fig. 4. As in the example of Fig. 4. The stopper component 318" is placed onto the shaft 312'. For this purpose, the shaft 312' has a pin 312a' which engages in a recess 318a' of the stopper component 318". In contrast to Fig. 4 is in the example of Fig. 12 a reversal of the pin connection between the shaft component 318" and the housing cover 346 is realized. In this embodiment, the housing cover 346 has a pin 448' on its inner surface facing the stop component 318" which now engages in an opening 350 of the stop component 318" and is preferably positively locked or materially locked there.

[0127] Fig. Figure 13 shows an enlarged section through another modified embodiment of a spindle motor similar to that in Fig. 5 is shown. For Fig. 13. The general description of the spindle motor applies. Fig. 5. As in the example of Fig. 5 The stopper component 418" is mounted on the shaft 412. The stopper component 418" has a pin 418a pointing downwards towards the shaft 412. This pin 418a is received in a blind bore 412b of the shaft 412. In contrast to Fig. 5 is in the example of Fig. 13 a reversal of the pin connection between the shaft component 418" and the housing cover 346 is realized. In this embodiment, the housing cover 346 has a pin 448' on its inner surface facing the stop component 418" which now engages in an opening 350 of the stop component 418" and is preferably positively locked or materially locked there.

[0128] Fig. Figure 14 shows a modified and enlarged representation of the spindle motor of Fig. 1 in the area of ​​the stopper component.

[0129] Unlike Fig. 1. No pin connection is provided between the shaft 12' and the housing cover 246. Instead, the end face of the shaft 12' rests against the housing cover 246 and is bonded to it, for example, by an adhesive bond or a weld. The stopper component 18 is fixedly connected to the shaft 12' and its end face also rests against the housing cover 246. Preferably, the stopper component 18 and the housing cover 246 are also bonded to each other by means of an adhesive bond or a weld. Furthermore, it can be provided that only the upper end face of the stopper component 18 or only the upper end face of the pin 12a' of the shaft 12' rests against the housing cover and is bonded to it (not shown in the drawing, this also applies in particular to the embodiments according to the Fig. 15 and Fig. 16).

[0130] Fig. Figure 15 shows a modified and enlarged representation of the spindle motor of Fig. 2 in the area of ​​the stopper component.

[0131] Unlike Fig. 2. No pin connection is provided between the shaft 112' and the housing cover 246. Instead, the end face of the shaft 112' rests against the housing cover 246 and is bonded to it by means of a material bond, for example, by an adhesive bond or weld. The stopper component 118 is firmly connected to the shaft 112' and its end face also rests against the housing cover 246. Preferably, the stopper component 118 and the housing cover 246 are also bonded to each other by means of an adhesive bond or weld.

[0132] Fig. Figure 16 shows a modified and enlarged representation of the spindle motor of Fig. 3 in the area of ​​the stopper component.

[0133] Unlike Fig.3. No pin connection is provided between the shaft 112' and the housing cover 246. Instead, the end face of the shaft 112' rests against the housing cover 246 and is bonded to it by a material bond, for example, by an adhesive bond or weld. The stopper component 218 is firmly connected to the shaft 112' and its end face also rests against the housing cover 246. Preferably, the stopper component 218 and the housing cover 246 are also bonded to each other by means of an adhesive bond or weld. List of reference symbols 10 Base plate 12, 12' Wave 112, 112', 312, 312', 412, 512, 612, 712, 812 12a, 12a' Cone 112a, 112a', 312a, 312a', 712a 412b Blind hole 14 Rotor component 114, 214, 314 114a Recess 214a 16 Bearing component 516, 616, 716, 816 516a first part 616a, 716a, 816a, 516b second part 616b, 716b, 816b 18 Stopper component 118, 218, 318, 318', 318", 418, 418', 418" 318a blind hole 318a', 418a, 418a' 318b Cone 418b 20 bearing gap 22 radial bearings 23 bearing groove structures 24 radial bearings 25 bearing groove structures 26 Separator gap 28 axial bearings 29 bearing groove structures 30 Recirculation channel 32 Cover 132, 232 34 Sealing gap 36 Sealing gap 38 Pump seal 138 39 pump groove structures 139 40 Rotary axis 42 Stator arrangement 44 Rotor magnet 46 Housing covers 146, 246, 346 48 pens 148, 448' 50 opening 150, 350 52 recess Level 660 562 weld seam 662, 762, 862

Claims

[1] Low-profile spindle motor comprising: a stationary motor component with a shaft component (12, 16, 18), wherein the shaft component (12, 16, 18) has a cylindrical shaft (12) with two ends, wherein a bearing component (16) is arranged at one end of the shaft (12) and a stop component (18) is arranged at the other end of the shaft (12), a rotatable motor component (14), a fluid dynamic bearing system (22, 24, 28) for the rotary bearing of the rotatable motor component (14) relative to the stationary motor component, an electromagnetic drive system (42, 44) for driving the rotatable motor component (14) about a rotary axis (40), and a housing cover (46) for closing the spindle motor, wherein the shaft component (12, 16, 18) is connected to the housing cover (46) by means of a pin connection or a purely material-bonded connection, characterized by, that the bearing component (516; 616) consists of a first part (516a; 616a) and a second part (516b, 616b), wherein the first part (516a; 616a) is formed integrally with the shaft (512; 612) and forms an axial bearing surface, and the second part (516b, 616b) is materially bonded to the first part (516a; 616a). [2] Spindle motor according to claim 1, characterized by , that the stopper component (18; 118; 218) is ring-shaped and is mounted on the shaft (12; 112) and is connected to the shaft (12, 112) by means of a force-fit and / or material-fit connection. [3] Spindle motor according to one of claims 1 or 2, characterized by that the pin connection is a positive-locking connection. [4] Spindle motor according to one of claims 1 or 2, characterized by that the pin connection is a force-fit connection. [5] Spindle motor according to one of claims 1 or 2, characterized bythat the pin connection is a material-bonded connection. [6] Spindle motor according to any one of claims 1 to 5, characterized by , that a free end of the shaft component (12, 16, 18) has a pin (48) which is aligned parallel to the axis of rotation (40) and is received in an opening (50) of the housing cover (46). [7] Spindle motor according to claim 6, characterized by , that the pin (48; 148) is arranged on an end face of the shaft (12, 112) facing the housing cover (46). [8] Spindle motor according to any one of claims 1 to 5, characterized by , that the housing cover (346) has a pin (448') on a surface facing the shaft component (412, 418"), which is received in an end-face opening (350) of the shaft component (412, 418"). [9] Spindle motor according to one of claims 1 or 2, characterized by, that in the case of a purely material-bonded connection the housing cover (246) lies flat on a flat end face of the shaft component (318'; 418'). [10] Spindle motor according to any one of claims 1 to 9, characterized by , that the stopper component (318) is designed in the form of a cap and has a central opening (318a; 318a´) on an end face, wherein the shaft (312) has a pin (312a; 312a´) on an end face facing the stopper component (318) which engages in the opening (318a; 318a´) of the stopper component (318) and is connected to the stopper component (318) by means of a force-fit and / or material-fit connection. [11] Spindle motor according to any one of claims 1 to 9, characterized by, that the stopper component (418; 418'') is designed in the form of a cap and has a central pin (418a) on one end face facing the shaft (412), wherein the shaft (412) has an opening (412b) on one end face facing the stopper component (418; 418''), into which the pin (418a) of the stopper component (418; 418'') engages and is connected to the shaft (412) by means of a force-fit and / or material-fit connection. [12] Spindle motor according to one of claims 10 to 11, characterized by , that a pin (318b; 448) is arranged on an end face of the stopper component (318; 418) facing the housing cover (46). [13] Spindle motor according to one of claims 10 to 11, characterized by , that the opening (350) for receiving the pin (448') is arranged on an end face of the stopper component (318"; 418") facing the housing cover (146). [14] Spindle motor according to any one of claims 1 to 13, characterized by, that a cover (32; 132; 232) is arranged on the rotatable motor component (14;114; 214), which covers an open end of the fluid dynamic bearing system and surrounds the stopper component (18; 118; 218) in a ring shape, wherein the cover (32; 132; 232) is U-shaped in cross-section or designed as a flat annular disk. [15] Spindle motor according to any one of claims 1 to 14, characterized by , that the shaft (12; 112; 212; 312; 412) has a step on which the stopper component (18; 118; 218; 318; 418) rests. [16] Low-profile hard disk drive comprising at least one storage disk which can be rotated by a spindle motor according to any one of claims 1 to 15 and a read / write device for writing and reading data to and from the storage disk.

Images