JP2000316240A - Stator for spindle motor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To install a stator for spindle motors with high efficiency in excitation, with accuracy in terms of dimensions and shape, and without possible damages to coils, and to provide a low cost manufacturing method of the stator. SOLUTION: A ferromagnetic material powder is injection-molded and sintered. A closed magnetic circuit ring is molded integrally with teeth 3, which protrude therefrom outward in the radial direction and placed at equal intervals in the circumferential direction, and are smaller in thickness than the closed magnetic circuit ring, and hammers which are formed at the outer ends of the teeth and are larger in thickness and width than in the teeth. An H-shaped stator core having deep coil spaces 9 is formed with the hammers, teeth 3, and a closed magnetic circuit ring, and coils 8 are wound in the coil spaces 9 to form a stator 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stator for a spindle motor, and more particularly to a small spindle motor stator for a hard disk drive and an apparatus for manufacturing the same.

[0002]

2. Description of the Related Art A permanent magnet type spindle motor has, for example, an 8-pole, 12-slot or a 6-pole or 12-pole, 9-slot structure.
It is formed by laminating a thin plate-shaped stator core plate consisting of a central closed magnetic path disk portion, radially extending tooth portions therefrom and a hammer formed at the tip thereof, and a coil is mounted on the laminated tooth portions. The winding forms a stator. The reason for stacking the stator core plates in this way is to avoid losses due to eddy currents.
0.35 mm or 0.2 mm silicon steel is used.

[0003] As described above, in the stator core formed by stacking the stator core plates, the total thickness is limited to an integral multiple of the thickness of one stator core plate, and the thickness of the stator core at all locations is limited. However, there is a problem that the area of the outer peripheral surface of the hammer cannot be increased so much, and the accumulated error of the thickness of the stator core increases as a result of laminating the plates.

Further, since the stator core plate is formed by punching, a sharp edge is formed, which may damage the coil wound around the teeth. Further, the coil wound around the teeth is exposed and easily damaged from the outside.

[0005] Incidentally, silicon steel is used as a material for the stator core plate, but this material is not the best material because its magnetic saturation rate is not high. In this respect, for example, a cobalt steel having a high cobalt content is desirable, but since a large amount of waste is generated by punching, use of this expensive material has a problem in manufacturing cost.

[0006] Further, as for the stator of a small spindle motor, the thickness of the stator core is reduced and the number of laminated stator core plates is reduced, so that the stator core may be one or two. Therefore, ・ The thickness of the core is limited, so that an appropriate thickness cannot always be obtained. ・ Because the number of laminations is small, loss due to eddy current is hardly avoided and there is no lamination effect. ・ The stator core and permanent magnet However, there is also a problem that the magnetic flux between them is reduced because the matching between them cannot be achieved.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a stator for a spindle motor in which a magnetic flux generated between a hammer of a stator core and a permanent magnet is increased, in particular, a small spindle motor for a hard disk drive and its manufacture. Is to provide a way.

Another object of the present invention is to provide a spindle motor which can be manufactured with high precision and at low cost, and a method of manufacturing the same.

Still another object of the present invention is to wind a coil of a stator core of a spindle motor around a tooth portion without damaging it, and to house the coil so as to be protected from the outside.

[0010]

In order to solve the above problems, a spindle motor stator according to the present invention comprises:
An annular closed magnetic path ring, a plurality of teeth protruding radially outward from the outer periphery of the closed magnetic path ring and equally arranged in a circumferential direction, and teeth opposed to a permanent magnet of a rotor coaxial with the closed magnetic path ring And a coil wound around the teeth, and the stator core is integrally formed of a ferromagnetic material as a single component. It is constituted by. The stator core is formed by injection molding as described later.

[0011] The closed magnetic path ring is formed thicker than the teeth, and the width and thickness of the hammer are formed larger than the width and thickness of the teeth to form an H-shaped stator core. Then, a coil space for receiving the coil is formed by the closed magnetic path ring, the teeth, and the hammer.

The thickness of the closed magnetic circuit ring and the width and thickness of the hammer are preferably such that the coil space completely accommodates the entire coil.

Preferably, the end face of the hammer is rectangular or square, the teeth have a substantially rectangular or square cross section, the ridges between the sides of the teeth are rounded, and the teeth are The transition between the hammer and the closed magnetic circuit ring is preferably formed in a radius, and the teeth preferably have a circular or elliptical cross section.
Preferably, the ferromagnetic material is made of cobalt steel.

A radially inwardly extending flange is integrally formed with the closed magnetic path ring at one end of the closed magnetic path ring, and the flange is a bearing pedestal that carries a corresponding end of the bearing assembly. It may be configured to hold the bearing assembly.

The method of manufacturing a stator for a spindle motor according to the present invention comprises an annular closed magnetic circuit ring, a plurality of teeth projecting radially outward from the outer periphery of the closed magnetic circuit ring and equally arranged in the circumferential direction; A stator core having a hammer formed on the outer periphery of the tooth portion facing the permanent magnet of the rotor coaxial with the path ring and having an outer circumferential surface larger than the cross section of the tooth portion; and a coil wound on the tooth portion. The stator core is formed by, for example, injection molding and sintering a powder of a ferromagnetic material such as cobalt steel. At this time, the above-mentioned flange is formed simultaneously with the stator core.
The stator core is precisely injection molded so that no post processing is required.

In this case, this manufacturing method includes a step of preparing a precise injection molding die for a stator to be manufactured, and a step of melting an injection molding material obtained by mixing a cobalt steel powder and a binder to form a mold. Injection molding, cooling the injection molded product in a mold, transferring the cooled injection molded product into a furnace, heating and removing the binder from the injection molded product (this process may be omitted). Can), sintering the injection molded article in a furnace, cooling the sintered injection molded article,
It is desirable to comprise a step of coating a sintered injection molded article with an electrical insulating material and a step of winding a coil around the teeth of the stator core formed by these steps.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the structure of a stator for a spindle motor according to the present invention will be described, and then a method of manufacturing the same will be described.

FIG. 1 is a plan view of one embodiment of a stator for a spindle motor according to the present invention, and FIG.
It is II sectional drawing, and a coil is abbreviate | omitted in both figures.

As shown in FIGS. 1 and 2, the stator 1 comprises:
It comprises a stator core 22 and a coil (not shown). The stator core 22 has a closed magnetic path ring 6 coaxial with its axis 7 and a flange 2 extending radially inward from the inner peripheral surface thereof and coaxial with the axis 7 of the stator 1. If necessary, a bearing (not shown) for holding the stator 1 on a shaft (not shown) or the like can be incorporated in the annular space 16 in the inner peripheral surface of the closed magnetic circuit ring 6. The spindle motor is, for example, a small one in which the outer shape of the stator 1 is 11 mm and the diameter of the annular space 16 is about 6 mm.

From the outer peripheral surface of the closed magnetic circuit ring 6, a plurality of teeth 3
Extend radially outward. The teeth 3 are equally arranged in the circumferential direction, the cross section is substantially rectangular or square, and a hammer 4 whose outer peripheral surface is substantially rectangular or square is formed at the outer peripheral end of each tooth 3. ing.

As shown in FIG. 1, the hammer 4 has a width wider than the width of the teeth 3 (this is the same as the conventional one). It protrudes in the direction. As shown in FIG. 2, the hammer 4 is formed to be thicker than the thickness of the tooth portion 3 unlike the conventional one, and protrudes from both side surfaces of the tooth portion 3 in the axial direction of the axis 7. Accordingly, the outer peripheral surface of the hammer 4 has a larger area than the cross section of the tooth portion 3 by the amount of protrusion in both directions of the shaft center 7, and accordingly, the outer peripheral surface of the hammer 4 facing the permanent magnet of the rotor. And the magnetic flux between the hammer 4 and the permanent magnet increases.

As shown in FIG. 2, the connecting portion between each tooth 3, the hammer 4 and the tooth 3 of the closed magnetic circuit ring 6 has an H-shape with a large lateral width, and a coil space surrounding the tooth 3 (for winding). Groove). If the coil is wound so as to be completely housed in this coil space, the coil will not jump out of the stator and it will not be possible to access the coil from outside, so the coil will be sufficiently Will be protected.

The transition between the adjacent ridges of the teeth 3 and the hammer 4 and the closed magnetic circuit ring 6 is rounded to prevent damage to the coils hitting them.

1 and 2 show the case where the teeth 3 are long. In this case, since the coil becomes longer, the thickness of the coil can be reduced in order to generate a necessary magnetic flux, and thus the toothed portion 3 can be made thinner, so that the spindle motor can be made thinner. it can.

However, when it is necessary to generate a larger magnetic flux in the coil, or when it is necessary to reduce the diameter of the spindle motor and thus the stator, it is necessary to wind the coil around the teeth 3 thickly. In this case, there is a disadvantage that the thickness of the stator is slightly increased. However, since the thickness of the hammer 4 can be increased to the height of the outer peripheral surface portion of the coil in both directions of the axis 7, the permanent shape of the rotor is reduced. There is a great merit that the outer peripheral area of the hammer 4 facing the magnet is greatly increased, and the magnetic flux generated between the two is greatly increased.

This is achieved in another embodiment shown in FIGS. FIG. 4 is a vertical sectional view taken along the line IV-IV of FIG. In these figures, the closed magnetic circuit ring is indicated by 14 and the hammer is indicated by 15.

As shown in FIG. 4, the stator core 22 of the stator 1 of the embodiment shown in FIG. 3 has a cylindrical closed magnetic path ring 14 and extends from the center of the outer periphery to the outside in the circumferential direction, and has a substantially cross-sectional shape. It comprises a rectangular or square tooth portion 3 and a hammer 15 formed integrally with the tooth portion 3 at the center of the inner surface at the outer end thereof. The flange 2 that extends inward in the axial direction is formed at the lower end of the inner peripheral surface of the closed magnetic path ring 14.

As shown in FIG. 3, the hammer 15 extends from the upper and lower surfaces of the teeth 3 to the height of the outer circumferential surface of the coil 8 in both axial directions of the axis 7 of the stator 1 or the height of the outer circumferential portion of the coil 8. As a result, the area of the opposing surface (outer peripheral surface) of the hammer 15 that faces the permanent magnet 12 of the rotor is significantly larger than the cross-sectional area of the tooth portion 3. Therefore, the hammer 15
In the annular space 17 between the outer peripheral surface and the permanent magnet 12, the magnetic flux generated therebetween expands and increases as indicated by 10 and 11. Although the direction of the magnetic flux is shown from the hammer 15 to the permanent magnet 12, it is reversed by a change in polarity. A thick coil 8 is wound around the tooth portion 3.

The upper and lower ends of the closed magnetic path ring 14 are also set to the height of the corresponding outer peripheral surface of the coil 8 or a height exceeding the height.
The closed magnetic path ring 14, the teeth 3, and the hammer 15 are formed in a high H shape, thereby forming a deep coil space (winding groove) 9 surrounding the teeth 3. For this reason, the coil 8
The coil 8 wound around the tooth portion 3 has a coil space 9
, And is hard to access from the outside of the stator 1, so that it is protected from breakage. In addition, as shown in FIG.
Are transition portions 18 and 19 between the teeth 3 and the closed magnetic circuit ring 14 and the hammer 15 as shown in FIG.
Are round, and the coils 8
No part is damaged. In the above two embodiments, the cross section of the tooth portion 3 has been described as a rectangle or a square, but may be substantially circular or elliptical.

FIG. 5 shows an embodiment of a spindle motor to which the stator 1 of FIG. 3 is attached. Base plate 23
The stator 1 is fixed to the base plate 23 by inserting the lower end of the closed magnetic circuit ring 14 into the hole 24 formed in the base plate 23.
The rotor 25 has a central shaft 26, and the central shaft 2
6 is inserted into a center hole formed by the inner peripheral surface of the stator 1, and is disposed coaxially and rotatably with respect to the stator 1.

A bearing assembly 29 comprising upper and lower two rolling bearings 27 and 28, such as ball bearings, between the inner peripheral surface of the stator 1 and the outer peripheral surface of the central shaft 26 of the rotor 25.
The outer peripheral surface of the outer ring of each bearing 27, 28 is fitted to the inner peripheral surface of the closed magnetic ring 14 of the stator 1, and the lower end surface of the outer ring of the lower bearing 28 is closed magnetic ring. 14
In contact with the flange 2. Therefore, the flange 2 is a bearing seat. Further, the inner peripheral surface of the closed magnetic circuit ring 14 serves to hold the bearing assembly 29. The bearing assembly 29 is loaded with a predetermined preload.

The stator core and the stator described above are manufactured as follows. 1) First, a mold for precise injection molding of a manufactured stator is prepared. 2) An injection molding material in which a powder or granules of a ferromagnetic material is mixed with a binder is melted and injection molded in the mold. 3) Cool the injection molded article in the mold. 4) The cooled injection molded product is transferred into a furnace and heated to remove the binder from the injection molded product. 5) Sinter the injection molded product in a furnace. 6) Cool the sintered injection molding. 7) coating the sintered injection molded article with an electrical insulating material. 8) A coil is wound around the teeth of the stator core formed in the steps 1) to 7). However, if it is not necessary to remove the binder, step 4 is not performed.

The ferromagnetic material is preferably a cobalt steel, particularly a cobalt steel having a cobalt content of 50% or more. As described above, such a cobalt steel is expensive, but when powder or granules are formed by injection molding, no debris is produced, so that the production of the stator core is profitable and the production of the stator core is simplified. Examples of this cobalt steel include Vacuum Schmeltze of Hanau, Germany.
Valcoflux 50 products from Bacum Schmeltze
There is.

The binding is, for example, a plastic material,
The injection-molded material thus formed is in the form of a sponge, and after the binding is removed in the furnace as described above,
Sintered to form a stator core. The stator core thus finished is reduced by, for example, 15% from the beginning, and the metal solid content accounts for 95% to 98% of the whole.

The ferromagnetic material is not limited to the above, but may be one that can be injection-molded or one that can be cast. The bind may be not only one that can be removed by heating, but also one that is eluted with a solvent.

The stator core manufactured by the above-described method is precisely finished, so that no post-processing is required. Therefore, there is an advantage that the manufacturing cost can be kept low and the shape and dimensions of the stator core can be selected with a large degree of freedom.

Since the stator core of the conventional spindle motor is formed by laminating a plurality of core plates,
The error in the lamination thickness could not be reduced to 1/10 mm. However, according to the present invention, as a result of the precision finishing of the stator core, the thickness error of the tooth portion is reduced to 1/10 m.
m, which is advantageous in that the operation performance of the small spindle motor is improved.

In the spindle motor according to the present invention, the thickness of the hammer can be made sufficiently large, and the amount of magnetic flux between the hammer and the permanent magnet of the rotor can be increased.
Another feature is that the matching between the hammer and the permanent magnet can be enhanced to cope with a high switching frequency in the air gap.

Therefore, the stator or stator core according to the present invention has a diameter of up to 30 mm-40 mm, for example.
Height 10 mm or lower, rotation speed 5,000
It is suitable as a stator or a stator core of a small spindle motor such as a multi-pole spindle motor of 0 rpm-20,000 rpm.

Although the present invention has been described with reference to an outer race stator, the present invention can be similarly applied to an inner race stator.

[0041]

According to the present invention, the stator core of a spindle motor, in particular, a small-sized spindle motor can be thinned and formed with high precision, and the magnetic flux between the hammer and the permanent magnet of the rotor can be expanded and increased. This has the effect of increasing the excitation effect. In addition, since the stator core is manufactured by injection molding, there is an effect that an expensive cobalt steel can be used as the material thereof with almost no increase in cost. Further, there is an effect that a coil space for a large coil can be formed to protect the coil.

[Brief description of the drawings]

FIG. 1 is a plan view of one embodiment of a spindle motor stator according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a right half axial sectional view of another embodiment of the spindle motor stator according to the present invention.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

5 is a longitudinal sectional view of one embodiment of a spindle motor to which the stator shown in FIG. 3 is attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator 2 Flange 3 Teeth 4 Hammer 5 Slot 6 Closed magnetic circuit ring 7 Axis 8 Coil 9 Coil space 10 Magnetic flux 11 Magnetic flux 12 Permanent magnet 13 Ridge 14 Closed magnetic circuit ring 15 Hammer 16 Space 17 Annular space 18 Transition part 19 Transition part DESCRIPTION OF SYMBOLS 21 Air gap 22 Stator core 23 Base plate 24 Hole 25 Rotor 26 Central shaft 27 Bearing 28 Bearing 29 Bearing assembly

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) H02K 21/22 H02K 21/22 M (72) Inventor King Hock Lee Malaysia, 75200 Malacca, Pang Sapuri Kesidang Sekschen 2. Jalan Keshidang 2/8, 2-13

Claims (17)

[Claims] 1. An annular closed magnetic path ring, a plurality of teeth projecting radially outward from an outer periphery of the closed magnetic path ring and equally arranged in a circumferential direction, and a rotor coaxial with the closed magnetic path ring. A stator core comprising a hammer formed on the outer periphery of the tooth portion facing the permanent magnet and having an outer peripheral surface larger than the cross section of the tooth portion; and a coil wound on the tooth portion, the stator core comprising: A stator for a spindle motor, which is integrally formed of a ferromagnetic material as one component. 2. The device according to claim 1, wherein the closed magnetic path ring is formed thicker than the teeth, and the width and thickness of the hammer are formed larger than the widths and thicknesses of the teeth. Stator for spindle motor. 3. The method according to claim 3, wherein the stator core is provided with the closed magnetic path ring,
3. The stator coil space according to claim 2, wherein the teeth and the hammer form an H-shape in an axial cross section that receives the coil, and the closed magnetic path ring, the teeth and the hammer form a stator coil space. Stator for spindle motor. 4. The spindle motor according to claim 3, wherein the thickness of the closed magnetic path ring and the width and thickness of the hammer are such that the coil space completely accommodates the entire coil. Stator. 5. The stator for a spindle motor according to claim 1, wherein the end face of the hammer is substantially rectangular or square. 6. The tooth portion has a substantially rectangular or square cross section, and a ridge between the side surfaces of the tooth portion is formed in a radius, and the ridge between the tooth portion and the hammer and the closed magnetic path ring is formed. The stator for a spindle motor according to any one of claims 1 to 5, wherein the transition portion is formed in a radius. 7. The spindle motor stator according to claim 1, wherein the tooth portion has a circular or elliptical cross section. 8. The spindle motor according to claim 1, wherein a flange extending radially inward at one end of the closed magnetic path ring is formed integrally with the closed magnetic path ring. For stator. 9. The spindle motor according to claim 8, wherein the flange is a bearing pedestal carrying a corresponding end of a bearing assembly, and an inner peripheral surface of the closed magnetic path ring holds the bearing assembly. For stator. 10. The spindle motor stator according to claim 1, wherein the ferromagnetic material is made of cobalt steel. 11. An annular closed magnetic path ring, a plurality of teeth projecting radially outward from an outer periphery of the closed magnetic path ring and equally arranged in a circumferential direction, and a rotor coaxial with the closed magnetic path ring. A stator core comprising a hammer formed on the outer periphery of the tooth portion facing the permanent magnet and having an outer peripheral surface larger than the cross section of the tooth portion; and a coil wound on the tooth portion, the stator core comprising: A method for manufacturing a stator for a spindle motor, wherein the ferromagnetic material powder is formed by injection molding and sintering. 12. The method for manufacturing a stator for a spindle motor according to claim 11, wherein said stator core is precisely finished so that post-processing of dimensions and shape is not required. 13. A method for manufacturing a stator for a spindle motor according to claim 11, wherein a flange extending radially inward at one end of said closed magnetic path ring is injection-molded integrally with said closed magnetic path ring. . 14. The spindle motor according to claim 13, wherein the flange is a bearing pedestal carrying a corresponding one end of a bearing assembly, and an inner peripheral surface of the closed magnetic path ring holds the bearing assembly. Of manufacturing stator for automotive. 15. A step of preparing a precision injection molding die for a stator to be manufactured, and 2) melting an injection molding material obtained by mixing a ferromagnetic powder and a binder to form a mold. 3) a step of cooling the injection molded article in the mold; 4) a step of sintering the injection molded article in a furnace; 5) a step of sintering the injection molded article. A step of cooling; 6) a step of coating the sintered injection molded article with an electric insulating material; and 7) winding the coil around the teeth of the stator core formed by the steps 1) to 6). A method for manufacturing a stator for a spindle motor, comprising: 16. Between the step of cooling the injection molded product in the mold and the step of sintering the injection molded product in the furnace, the cooled injection molded product is transferred into a furnace and heated. The method for manufacturing a stator for a spindle motor according to claim 15, wherein a step of removing a binder from the injection molded product is performed. 17. The method according to claim 11, wherein the ferromagnetic material is made of cobalt steel.