JP2008169940A - Magnetic fluid bearing and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic fluid bearing having excellent durability and stable bearing performance while improving a slide characteristic, and its manufacturing method. <P>SOLUTION: This magnetic fluid bearing 1 is provided with a fixed shaft 2, an outer ring sleeve 4 arranged at the outer periphery of the fixed shaft 2, and a magnetic fluid 7 injected between the fixed shaft 2 and the outer ring sleeve 4. A thrust bearing and a radial bearing are composed between the fixed shaft 2 and the outer ring sleeve 4. The fixed shaft 2 has an insert 9 having a female screw formed on the inner peripheral surface, and a shaft body 10 arranged to cover the outer peripheral surface of the insert 9. A plurality of magnetic poles are formed on the outer peripheral surface of the fixed shaft 2. The shaft body 10 is formed of resin, and the insert 9 is formed of a material having hardness higher than that of the shaft body 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic fluid bearing and a manufacturing method thereof, and more particularly to a magnetic fluid bearing used as a fulcrum bearing of a swing arm of a hard disk and a manufacturing method thereof.

  The magnetic fluid bearing is a bearing using magnetic fluid as a lubricant for the bearing. Since the operation principle of magnetic fluid bearings is based on magnetic force regardless of fluid lubrication theory, external pressure is applied even when the shaft and outer ring are relatively stationary or when the relative speed between the shaft and outer ring is extremely small. Without this, the shaft and the outer ring can be supported in a non-contact manner. Moreover, since magnetic fluid also has viscosity, it can give a high damping property to a bearing. For this reason, the magnetic fluid bearing is suitable as a fulcrum bearing for swinging motion, and can be used as a fulcrum bearing for a swing arm of a hard disk (HDD) of a computer.

  FIG. 14 is a cross-sectional view showing a configuration of a conventional magnetic fluid bearing. Referring to FIG. 14, a magnetic fluid bearing 101 is used as, for example, a fulcrum bearing of an HDD swing arm, and has a fixed shaft 102 having a magnetic pole forming portion 103, an outer ring sleeve 104, a thrust plate 105, and a magnetic fluid 107. And.

  The fixed shaft 102 has a cylindrical shape with a hollow portion 108, a disk-shaped thrust plate 105 is fixed to the upper end portion of the fixed shaft 102, and a disk-shaped flange portion is formed on the lower end portion of the fixed shaft 102. 106 is provided. The thrust plate 105 is fixed to the fixed shaft 102 by bonding, and the flange portion 106 is formed integrally with the fixed shaft 102. The thrust plate 105 and the flange portion 106 extend in a direction perpendicular to the fixed shaft 102 (lateral direction in the figure). Further, a female screw is formed on the inner peripheral surface of the hollow portion 108, and the magnetic fluid bearing 101 is fixed to the HDD (not shown) by screwing a male screw (not shown) into the female screw.

  A magnetic pole forming portion 103 is provided on the outer periphery of the fixed shaft 102. A plurality of magnetic poles are formed in the magnetic pole forming portion 103. A recess 111 is formed on the outer periphery of the fixed shaft 102 by the thrust plate 105, the fixed shaft 102, and the flange portion 106.

  The outer ring sleeve 104 has a hollow shape and is disposed on the outer periphery of the fixed shaft 102 with a bearing gap therebetween. The outer ring sleeve 104 is rotatable with respect to the fixed shaft 102. The outer ring sleeve 104 has a convex portion 112 protruding in the inner diameter direction, and the convex portion 112 and the concave portion 111 are opposed to each other. A magnetic fluid 107 is injected between the convex portion 112 and the concave portion 111.

  The outer ring sleeve 104 is held in the thrust direction by the thrust plate 105 and the flange portion 106. The outer ring sleeve 104 and the thrust plate 105, and the outer ring sleeve 104 and the flange portion 106 constitute a thrust bearing. The outer ring sleeve 104 and the fixed shaft 102 constitute a radial magnetic fluid bearing.

In addition to the structure shown in FIG. 14, conventional magnetic fluid bearings include, for example, Japanese Patent Application Laid-Open No. 2004-218792 (Patent Document 1), Japanese Utility Model Publication No. 7-736 (Patent Document 2), and Japanese Patent Application Laid-Open No. 2003-13957. It is disclosed also in the gazette (patent document 3).
JP 2004-218792 A No. 7-736 JP 2003-13957 A

  In particular, a magnetic fluid bearing used as a fulcrum bearing for a swing arm of an HDD is required to have good sliding characteristics. One method for improving the sliding characteristics is to form the fixed shaft 102 and the thrust plate 105 with resin instead of metal. Since the resin has a smaller coefficient of friction than metal, the friction between the outer ring sleeve 104 and the thrust plate 105 and the outer ring sleeve 104 and the flange portion 106 is reduced.

  However, if the fixed shaft 102 is formed of resin, the strength of the fixed shaft 102 is reduced. If the strength of the fixed shaft 102 is low, the internal thread of the hollow portion 108 may be deformed or broken due to vibration from the outside of the HDD or heat generation of the HDD. In addition, since a load is applied to the female screw when the male screw is screwed into the female screw on the inner peripheral surface of the hollow portion 108, the female screw may be deformed if the strength of the fixed shaft 102 is low. As described above, when the fixed shaft 102 is formed of resin in order to improve the sliding characteristics, there is a problem that durability is lowered and bearing performance becomes unstable.

  Accordingly, an object of the present invention is to provide a magnetic fluid bearing having improved durability and stable bearing performance while improving sliding characteristics, and a manufacturing method thereof.

  The magnetic fluid bearing of the present invention includes a shaft, an outer ring disposed on the outer periphery of the shaft, and a magnetic fluid injected between the shaft and the outer ring. A thrust bearing and a radial bearing are formed between the shaft and the outer ring. The shaft has an inner part in which an internal thread is formed on the inner peripheral surface, and an outer part arranged so as to cover the outer peripheral surface of the inner part. A plurality of magnetic poles are formed on the outer peripheral surface of the shaft or the inner peripheral surface of the outer ring. The outer portion is made of resin, and the inner portion is made of a material having a hardness higher than the hardness of the outer portion.

  The magnetic fluid bearing manufacturing method of the present invention includes a shaft, an outer ring disposed on the outer periphery of the shaft, and a magnetic fluid injected between the shaft and the outer ring, and a thrust is provided between the shaft and the outer ring. A magnetic fluid bearing manufacturing method in which a bearing and a radial bearing are configured. The method of manufacturing a magnetic fluid bearing according to the present invention includes a shaft step for manufacturing a shaft, a step for manufacturing an outer ring, a step of forming a plurality of magnetic poles on the outer peripheral surface of the shaft or the inner peripheral surface of the outer ring, A step of arranging on the outer periphery, and a step of injecting a magnetic fluid between the shaft and the outer ring. The shaft process includes a step of forming the outer portion with a resin, a step of forming an inner portion with an internal thread formed on the inner peripheral surface with a material having a hardness higher than the hardness of the outer portion, and an outer peripheral surface of the inner portion on the outer side. And a covering step of covering with a part.

  According to the magnetic fluid bearing and the manufacturing method thereof of the present invention, since the inner portion where the female screw is formed is made of a material having high hardness, deformation and breakage of the female screw due to vibration and heat of the shaft can be suppressed. It is possible to suppress deformation of the female screw when the male screw is screwed into the female screw. As a result, a magnetic fluid bearing having excellent durability and stable bearing performance can be obtained. In addition, since the outer portion is made of resin, the friction between the outer ring and the shaft is reduced, and the sliding characteristics can be improved.

  In the magnetic fluid bearing of the present invention, preferably, the outer portion is made of at least one selected from the group consisting of tetrafluoroethylene resin, polyacetal, polyamide, polyethylene, polyimide, polyphenylene sulfide, and polyetheretherketone. These materials are suitable as materials for the outer part because of their particularly low coefficient of friction.

  Preferably in the manufacturing method, in the covering step, the outer peripheral surface of the inner portion and the inner peripheral surface of the outer portion are screwed together.

  In the manufacturing method, preferably, in the coating step, the outer portion is formed on the outer periphery of the inner portion by injection molding.

  According to the magnetic fluid bearing and the manufacturing method thereof of the present invention, a magnetic fluid bearing having excellent durability and stable bearing performance can be obtained while improving the sliding characteristics.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a cross-sectional view showing a configuration of a magnetic fluid bearing according to Embodiment 1 of the present invention. Referring to FIG. 1, the magnetic fluid bearing 1 in the present embodiment includes a fixed shaft 2 as a shaft, an outer ring sleeve 4 as an outer ring, a thrust plate 5, and a magnetic fluid 7. An outer ring sleeve 4 is disposed on the outer periphery of the fixed shaft 2 with a radial bearing gap therebetween. A magnetic fluid 7 is injected between the outer peripheral surface of the fixed shaft 2 and the inner peripheral surface of the outer ring sleeve 4. A disc-shaped thrust plate 5 is fixed to the upper end portion of the fixed shaft 2.

  A disc-shaped flange portion 6 is provided at the lower end portion of the fixed shaft 2. The flange portion 6 is formed integrally with the fixed shaft 2. Each of the thrust plate 5 and the flange portion 6 extends in a direction perpendicular to the fixed shaft 2 (lateral direction in the figure), and a recess 11 is formed by the thrust plate 5, the fixed shaft 2, and the flange portion 6. ing.

  The fixed shaft 2 has an insert 9 as an inner portion and a shaft body 10 as an outer portion. The insert 9 has a cylindrical shape with a hollow portion 8, and an internal thread is formed on the inner peripheral surface of the hollow portion 8. The shaft main body 10 has a cylindrical shape with the flange portion 6 extending, and is disposed so as to cover the outer peripheral surface of the insert 9.

  The magnetic pole forming part 3 has a cylindrical shape and is arranged on the outer peripheral surface of the shaft body 10 between the thrust plate 5 and the flange part 6.

  The shaft body 10 is made of resin, and the insert 9 is made of a material having a hardness (Vickers hardness) higher than the hardness of the shaft body 10. Specifically, the shaft body 10 is made of, for example, tetrafluoroethylene resin, polyacetal, polyamide, polyethylene, polyimide, polyphenylene sulfide, or polyether ether ketone. Since these materials have a particularly small coefficient of friction, the friction of the thrust bearing portion can be reduced. The insert 9 is made of a metal such as steel or aluminum.

  The outer ring sleeve 4 has a hollow cylindrical shape and is arranged to be rotatable about the fixed shaft 2. The inner peripheral surface of the outer ring sleeve 4 protrudes toward the inner diameter side and constitutes a convex portion 12. The convex portion 12 of the outer ring sleeve 4 and the concave portion 11 of the fixed shaft 2 face each other.

  2A is an enlarged view of part A in FIG. 1, and FIG. 2B is an enlarged view of part B in FIG. 2A and 2B, the lower surface 5a of the thrust plate 5 and the axial upper end surface 4a of the convex portion 12 of the outer ring sleeve 4 are opposed to each other. Further, the outer peripheral surface 3b of the magnetic pole forming portion 3 (the outer peripheral surface 3b of the fixed shaft 2) and the inner peripheral surface 4b of the outer ring sleeve 4 are opposed to each other. Furthermore, the upper surface 6a of the flange portion 6 and the axial lower end surface 4c of the convex portion 12 of the outer ring sleeve 4 are opposed to each other. A magnetic fluid 7 is injected into a gap between the outer peripheral surface 3b of the fixed shaft 2 and the inner peripheral surface 4b of the outer ring sleeve 4, and the fixed shaft 2 and the outer ring sleeve 4 constitute a radial sliding bearing which is a magnetic fluid bearing. ing. In addition, the magnetic fluid 7 is also present in the gap between the lower surface 5a of the thrust plate 5 and the upper end surface 4a in the axial direction of the outer ring sleeve 4, and the gap between the upper surface 6a of the flange portion 6 and the lower end surface 4c in the axial direction of the outer ring sleeve 4. The outer ring sleeve 4 and the thrust plate 5, and the outer ring sleeve 4 and the flange portion 6 constitute a thrust sliding bearing by boundary lubrication.

  Each of the outer ring sleeve 4 and the thrust plate 5 is made of a nonmagnetic material such as austenitic stainless steel or brass. The magnetic pole forming portion 3 is made of a magnetic material such as ferrite. The magnetic fluid 7 is made of a liquid in which magnetic particles are dispersed in a colloidal form, for example. Further, for example, materials such as fatty acids, alcohols, aliphatic amides, esters, sulfurized fats and oils or derivatives of these materials (hereinafter sometimes referred to as lubricating materials) are in the range of 0.1% by mass to 3% by mass. It may be further added to the liquid. Since these lubricating materials are polar substances having a high adsorptivity to the metal surface and have a high lubricating ability, the lubricity of the magnetic fluid 7 can be improved.

  FIG. 3 is a diagram showing the magnetic pole distribution of the magnetic pole forming portion in the cross section taken along the line III-III in FIG. 1, and FIG. 4 is a diagram showing the magnetic pole distribution in the developed view of the magnetic pole forming portion. 3 and 4, a plurality of magnetic poles are formed on the magnetic pole forming portion 3 on the outer peripheral surface of the fixed shaft 2, and the plurality of magnetic poles are arranged in the circumferential direction (lateral direction in FIG. 4). Magnetized. Magnetic poles adjacent in the circumferential direction are different from each other, and each of the plurality of magnetic poles extends in the axial direction (vertical direction in FIG. 4).

  The magnetic pole forming portion 3 is free to be magnetized, and may be in a magnetized state as shown in FIG. 5 or 6 in addition to the magnetized state shown in FIGS. Referring to FIG. 5, the magnetic pole forming portion 3 is magnetized so that a plurality of magnetic poles are arranged in the axial direction. The magnetic poles adjacent in the axial direction are different from each other, and each of the plurality of magnetic poles extends in the circumferential direction. Referring to FIG. 6, the magnetic pole forming portion 3 is magnetized so that a plurality of magnetic poles are arranged in the axial direction and the circumferential direction. The magnetic poles adjacent to each other in the axial direction and the circumferential direction are different from each other.

  In the above description, the magnetic pole forming portion 3 is magnetized. However, instead of being magnetized, a hole is formed in the outer peripheral surface of the magnetic pole forming portion 3, and a permanent magnet is embedded in the hole. Also good. When the permanent magnet is embedded, the magnetic pole forming part 3 may be formed of resin integrally with the shaft body 10.

  Then, the manufacturing method of the magnetic fluid bearing 1 in this Embodiment is demonstrated using FIGS.

  First, referring to FIG. 7, the fixed shaft 2 is manufactured (shaft process). Specifically, the shaft body 10 is formed of resin. Further, the insert 9 having a female screw formed on the inner peripheral surface of the hollow portion 8 is formed of a material having a hardness higher than the hardness of the shaft body 10. Then, as indicated by an arrow in the figure, the insert 9 is inserted into the shaft body 10, and the insert 9 is fixed (for example, bonded) within the shaft body 10. The outer peripheral surface of the insert 9 and the inner peripheral surface of the shaft body 10 may be screwed together. Thereby, the outer peripheral surface of the insert 9 is covered with the shaft body 10.

  In addition, as a method of covering the outer peripheral surface of the insert 9 with the shaft body 10, for example, injection molding may be used in addition to the above-described method. Referring to FIG. 8, when injection molding is performed, insert 9 is placed in a sealed space formed by molds 31a and 31b. Then, a high-pressure resin 32 heated to a softening temperature is filled in the sealed space, and the resin is cooled and cured.

  Next, referring to FIG. 9, a plurality of magnetic poles are formed on the outer peripheral surface of the fixed shaft 2. Specifically, the magnetic pole forming portion 3 having a plurality of magnetic poles is fitted into the fixed shaft 2 as shown by arrows in the figure and fixed (for example, bonded). Note that the magnetic pole may be formed in the magnetic pole forming portion 3 after the magnetic pole forming portion 3 is fitted into the fixed shaft 2.

  Next, referring to FIG. 10, the outer ring sleeve 4 is manufactured. Then, the outer ring sleeve 4 is arranged on the outer periphery of the fixed shaft 2 as indicated by an arrow in the figure.

  Next, referring to FIG. 1, a magnetic fluid 7 is injected between the fixed shaft 2 and the outer ring sleeve 4. Thereafter, the thrust plate 5 is fixed (for example, bonded) to the upper portion of the fixed shaft 2, and the magnetic fluid bearing 1 is completed.

  The magnetic fluid bearing 1 in the present embodiment includes a fixed shaft 2, an outer ring sleeve 4 disposed on the outer periphery of the fixed shaft 2, and a magnetic fluid 7 injected between the fixed shaft 2 and the outer ring sleeve 4. ing. A thrust bearing and a radial bearing are configured between the fixed shaft 2 and the outer ring sleeve 4. The fixed shaft 2 includes an insert 9 having a female screw formed on the inner peripheral surface, and a shaft body 10 disposed so as to cover the outer peripheral surface of the insert 9. A plurality of magnetic poles are formed on the outer peripheral surface of the fixed shaft 2. The shaft body 10 is made of resin, and the insert 9 is made of a material having a hardness higher than that of the shaft body 10.

  The manufacturing method of the magnetic fluid bearing 1 in the present embodiment includes a fixed shaft 2, an outer ring sleeve 4 disposed on the outer periphery of the fixed shaft 2, and a magnetic fluid 7 injected between the fixed shaft 2 and the outer ring sleeve 4. And a magnetic fluid bearing manufacturing method in which a thrust bearing and a radial bearing are configured between the fixed shaft 2 and the outer ring sleeve 4. The manufacturing method of the magnetic fluid bearing 1 in the present embodiment includes a shaft process for manufacturing the fixed shaft 2, a process for manufacturing the outer ring sleeve 4, a process for forming a plurality of magnetic poles on the outer peripheral surface of the fixed shaft 2, and an outer ring. The method includes a step of arranging the sleeve 4 on the outer periphery of the fixed shaft 2 and a step of injecting the magnetic fluid 7 between the fixed shaft 2 and the outer ring sleeve 4. The shaft step includes a step of forming the shaft body 10 with a resin, a step of forming the insert 9 having an internal thread formed on the inner peripheral surface thereof with a material having a hardness higher than the hardness of the shaft main body 10, and an outer peripheral surface of the insert 9. And a covering step of covering with a shaft body 10.

  According to the magnetic fluid bearing 1 and the manufacturing method thereof in the present embodiment, since the insert 9 on which the female screw is formed is made of a material having high hardness, the female screw is deformed or damaged due to vibration or heat of the fixed shaft 2. It is possible to suppress the deformation of the female screw when the male screw is screwed onto the female screw. As a result, the magnetic fluid bearing 1 having excellent durability can be obtained. In addition, since the function of holding the fixed shaft 2 in a predetermined position is maintained, the magnetic fluid bearing 1 having stable bearing performance can be obtained. In addition, since the shaft body 10 is made of resin, the friction between the outer ring sleeve 4 and the fixed shaft 2 is reduced as compared with the case where the fixed shaft 2 is made of metal. In particular, since the thrust bearing portion constituted by each of the outer ring sleeve 4 and the thrust plate 5, and the outer ring sleeve 4 and the flange portion 6 is boundary lubrication, the sliding characteristics of these thrust bearing portions can be improved. .

  In the present embodiment, the upper end surface 9a of the insert 9 and the upper end surface 10a of the shaft body 10 are configured by the same plane, and the lower end surface 9b of the insert 9 and the lower end surface 10b of the shaft body 10 are The case where is constituted by the same plane is shown. In the present invention, in addition to such a case, as shown in FIG. 11, the upper end surface 9 a of the insert 9 may protrude outward from the upper end surface 10 a of the shaft body 10, or the lower end surface 9 b of the insert 9 may be The shaft main body 10 may protrude outward from the lower end surface 10b. Each of the upper end surface 9a and the lower end surface 9b of the insert 9 is configured in the same plane as each of the upper end surface 10a and the lower end surface 10b of the shaft body 10, or more than each of the upper end surface 10a and the lower end surface 10b of the shaft body 10. By projecting to the outside, the insert 9 comes into contact with the HDD case, and deformation of the shaft body 10 can be suppressed.

(Embodiment 2)
FIG. 12 is a cross-sectional view showing the configuration of the magnetic fluid bearing according to the second embodiment of the present invention. Referring to FIG. 12, ferrofluid bearing 1 in the present embodiment is the same as ferrofluid bearing in the first embodiment in that a plurality of magnetic poles are formed not on the outer peripheral surface of the shaft but on the inner peripheral surface of the outer ring. Is different. Specifically, the magnetic pole forming portion 3 is disposed on the inner peripheral surface of the outer ring sleeve 4 instead of being disposed on the outer peripheral surface of the fixed shaft 2.

  The magnetic pole forming part 3 may be formed separately from the outer ring sleeve 4 or may be formed integrally with the outer ring sleeve 4. When formed separately from the outer ring sleeve 4, the magnetized magnetic pole forming portion 3 may be bonded to the inner peripheral surface of the outer ring sleeve 4 or may be fitted to the inner peripheral surface of the outer ring sleeve 4. When formed integrally with the outer ring sleeve 4, the inner peripheral surface of the outer ring sleeve 4 made of a magnetic material may be magnetized, or a hole is formed in the inner peripheral surface of the outer ring sleeve 4, and a permanent magnet is formed in the hole. May be embedded.

  In addition, since the structure and manufacturing method of the magnetic fluid bearing 1 other than this are the same as the structure and manufacturing method of the magnetic fluid bearing in Embodiment 1 shown in FIG. 1, the same code | symbol is attached | subjected to the same member. The description will not be repeated.

  According to the magnetic fluid bearing 1 and the manufacturing method thereof in the present embodiment, the same effects as those of the magnetic fluid bearing and the manufacturing method thereof in the first embodiment can be obtained.

(Embodiment 3)
FIG. 13 is a cross-sectional view showing the configuration of the HDD swing arm device according to the third embodiment of the present invention. With reference to FIG. 13, the swing arm device 21 includes a magnetic fluid bearing 1 and a swing arm 22. As the magnetic fluid bearing 1, the one described in the first or second embodiment is used. The fixed shaft 2 is fixed to the base 23 by screwing a male screw 27 into the base 23 and the hollow portion 8 of the fixed shaft 2 of the magnetic fluid bearing 1. A swing arm 22 is attached to the outer ring sleeve 4 of the magnetic fluid bearing 1. As a result, the swing arm 22 can swing about the fixed shaft 2 (male screw 27). A magnetic head 24 for recording information on the magnetic disk 25 is provided at the left end of the swing arm 22 in the figure, and the magnetic head 24 faces the information recording surface of the magnetic disk 25. A rotor 26a of a head positioning mechanism 26 is provided at the right end of the swing arm 22 in the figure. The base 23 is provided with a stator 26b of the head positioning mechanism 26 so as to face the rotor 26a. The rotor 26a is constituted by a coil, and the stator 26b is constituted by a permanent magnet. In the swing arm device 21, a current is passed through the rotor 26 a to generate a force that swings the swing arm 22 and moves the magnetic head 24 to a desired position. In other words, the swinging motion of the swing arm 22 is servo-controlled by the head positioning mechanism 26 as a voice coil motor that is an actuator, and the magnetic head 24 is positioned.

  When the rotational direction is switched in the swinging motion of the swing arm 22, the rotational speed is always zero and there is a dead point. Furthermore, since the swing arm 22 is frequently started and stopped in the swing arm device 21, the rotational speed of the swing arm 22 becomes zero each time it is started and stopped. In the magnetic fluid bearing 1, the fixed shaft 2 and the outer ring sleeve 4 are always supported in a non-contact manner by the magnetic fluid filled between the outer periphery of the fixed shaft 2 and the inner periphery of the outer ring sleeve 4. It is suitable as a support structure for the swing arm of the arm device.

  The embodiment disclosed above should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above embodiments but by the scope of claims, and is intended to include all modifications and variations within the scope and meaning equivalent to the scope of claims.

  The magnetic fluid bearing and the manufacturing method thereof of the present invention are suitable as a magnetic fluid bearing used as a fulcrum bearing of a swing arm of a hard disk and a manufacturing method thereof.

It is sectional drawing which shows the structure of the magnetic fluid bearing in Embodiment 1 of this invention. (A) is the A section enlarged view of FIG. 1, (b) is the B section enlarged view of FIG. It is a figure which shows the magnetic pole distribution of the magnetic pole formation part in the cross section along the III-III line | wire of FIG. It is a figure which shows magnetic pole distribution in the expanded view of a magnetic pole formation part. It is a figure which shows the other example of the magnetic pole distribution in the expanded view of a magnetic pole formation part. It is a figure which shows the further another example of the magnetic pole distribution in the expanded view of a magnetic pole formation part. It is sectional drawing which shows the 1st process of the manufacturing method of the magnetic fluid bearing in Embodiment 1 of this invention. It is sectional drawing which shows the other example of the 1st process of the manufacturing method of the magnetic fluid bearing in Embodiment 1 of this invention. It is sectional drawing which shows the 2nd process of the manufacturing method of the magnetic fluid bearing in Embodiment 1 of this invention. It is sectional drawing which shows the 3rd process of the manufacturing method of the magnetic fluid bearing in Embodiment 1 of this invention. It is sectional drawing which shows the other structure of the magnetic fluid bearing in Embodiment 1 of this invention. It is sectional drawing which shows the structure of the magnetic fluid bearing in Embodiment 2 of this invention. It is sectional drawing which shows the structure of the swing arm apparatus of HDD in Embodiment 3 of this invention. It is sectional drawing which shows the structure of the conventional magnetic fluid bearing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,101 Magnetic fluid bearing, 2,102 Fixed shaft, 3,103 Magnetic pole formation part, 3b Magnetic pole formation part outer peripheral surface, 4,104 Outer ring sleeve, 4a Outer ring sleeve axial upper end surface, 4b Outer ring sleeve inner peripheral surface, 4c Outer ring Sleeve axial direction lower end surface, 5,105 Thrust plate, 5a Thrust plate lower surface, 6,106 Flange portion, 6a Flange portion upper surface, 7,107 Magnetic fluid, 8,108 Hollow portion, 9 Insert, 9a Insert upper end surface, 9b Insert Lower end surface, 10 shaft main body, 10a shaft main body upper end surface, 10b shaft main body lower end surface, 11, 111 concave portion, 12, 112 convex portion, 21 swing arm device, 22 swing arm, 23 base, 24 magnetic head, 25 magnetic disk , 26 Head positioning mechanism, 26a Rotor, 26b Stator, 27 Male thread, 31a 31b mold, 32 resin.

Claims (3)

The axis,
An outer ring disposed on the outer periphery of the shaft;
A magnetic fluid injected between the shaft and the outer ring,
A thrust bearing and a radial bearing are configured between the shaft and the outer ring,
The shaft has an inner part in which an internal thread is formed on an inner peripheral surface, and an outer part arranged so as to cover the outer peripheral surface of the inner part,
A plurality of magnetic poles are formed on the outer peripheral surface of the shaft or the inner peripheral surface of the outer ring,
The magnetic fluid bearing according to claim 1, wherein the outer portion is made of resin, and the inner portion is made of a material having a hardness higher than that of the outer portion.   The magnetic fluid bearing according to claim 1, wherein the outer portion is made of at least one selected from the group consisting of tetrafluoroethylene resin, polyacetal, polyamide, polyethylene, polyimide, polyphenylene sulfide, and polyetheretherketone. A thrust bearing and a radial bearing are configured between the shaft and the outer ring, comprising a shaft, an outer ring disposed on the outer periphery of the shaft, and a magnetic fluid injected between the shaft and the outer ring. A method of manufacturing a magnetic fluid bearing,
A shaft process for manufacturing the shaft;
Producing the outer ring;
Forming a plurality of magnetic poles on the outer peripheral surface of the shaft or the inner peripheral surface of the outer ring;
Arranging the outer ring on the outer periphery of the shaft;
Injecting the magnetic fluid between the shaft and the outer ring,
The shaft step includes a step of forming an outer portion with a resin, a step of forming an inner portion having a female screw on an inner peripheral surface thereof with a material having a hardness higher than the hardness of the outer portion, and an outer periphery of the inner portion. And a coating step of covering the surface with the outer portion.

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