JP2008082461A - Magnetic fluid bearing and swing arm device of hard disk having this magnetic fluid bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stably operable magnetic fluid bearing, and a swing arm device of HDD having this magnetic fluid bearing. <P>SOLUTION: This magnetic fluid bearing 1 has a cylindrical fixed shaft 2, a sleeve 4 arranged on the outer periphery of the fixed shaft 2 and having an inner peripheral surface opposed to an outer peripheral surface of the fixed shaft 2, a flange plate 5 threadedly engaging with the fixed shaft 2 in an upper end part of the fixed shaft 2 and having an under surface opposed to an upper end surface in the axial direction of the sleeve 4, and a magnetic fluid 7 injected into a clearance between the outer peripheral surface of the fixed shaft 2 and the inner peripheral surface of the sleeve 4 and a clearance between the upper end surface in the axial direction of the sleeve 4 and the under surface of the flange plate 5. A plurality of magnetic poles are formed on the outer peripheral surface of the fixed shaft 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic fluid bearing and a swing arm device of a hard disk provided with the magnetic fluid bearing.

  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. 11 is a cross-sectional view showing a configuration of a conventional magnetic fluid bearing. Referring to FIG. 11, magnetic fluid bearing 101 is used as a fulcrum bearing of a swing arm of an HDD, for example, and includes fixed shaft 102 having magnetic pole forming portion 103, sleeve 104, flange plate 105, and magnetic fluid 107. It has.

  The fixed shaft 102 has a cylindrical shape with a hollow portion 108, and a disk-shaped flange 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 flange 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 flange plate 105 and the flange portion 106 extend in a direction perpendicular to the fixed shaft 102 (lateral direction in FIG. 11).

  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 flange plate 105, the fixed shaft 102, and the flange portion 106.

  The sleeve 104 has a hollow shape and is disposed on the outer periphery of the fixed shaft 102 with a bearing gap therebetween. The sleeve 104 is rotatable with respect to the fixed shaft 102. The 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 sleeve 104 is held in the thrust direction by the flange plate 105 and the flange portion 106. Each of the sleeve 104 and the flange plate 105, and the sleeve 104 and the flange portion 106 constitutes a thrust bearing. The sleeve 104 and the fixed shaft 102 constitute a radial magnetic fluid bearing.

In addition to the structure shown in FIG. 11, 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

  The conventional ferrofluid bearing 101 is manufactured by fitting a flange plate 105 formed separately from the fixed shaft 102 to the fixed shaft 102 after fitting a sleeve 104 to the fixed shaft 102. However, since the area of the contact portion (attachment) c101 between the flange plate 105 and the fixed shaft 102 is small, it is not easy to bond the flange plate 105 to the fixed shaft 102. The flange plate 105 is not attached to the fixed shaft 102. It is easy to be fixed (bent) at a non-right angle. When the flange plate 105 is bent and fixed with respect to the fixed shaft 102, the flange plate 105 and the sleeve 104 are easily brought into solid contact. For this reason, the bearing could not be stably operated.

  Here, a method of increasing the area of the contact portion c101 by increasing the thickness (height) h101 of the flange plate 105 so that the flange plate 105 can be easily attached to the fixed shaft 102 is also conceivable. However, when the thickness h101 of the flange plate 105 is increased, the area of the magnetic pole forming portion 103 facing the sleeve 104 is reduced, the magnetic force for holding the magnetic fluid 107 is reduced, and the function as the magnetic fluid bearing is impaired. For this reason, increasing the thickness h101 of the flange plate 105 is not an effective method.

  Accordingly, an object of the present invention is to provide a magnetic fluid bearing that can be operated stably and a swing arm device of an HDD including the same.

  Another object of the present invention is to provide a magnetic fluid bearing that can be easily manufactured and a swing arm device of an HDD including the same.

  A magnetic fluid bearing according to the present invention includes a cylindrical shaft, an outer ring disposed on the outer periphery of the shaft and having an inner peripheral surface facing the outer peripheral surface of the shaft, and screwed with the shaft at the end of the shaft. And a magnetic fluid injected into the gap between the outer peripheral surface of the shaft and the inner peripheral surface of the outer ring and the gap between the axial end surface of the outer ring and the main surface of the plate. ing. A plurality of magnetic poles are formed on the outer peripheral surface of the shaft or the inner peripheral surface of the outer ring.

  According to the magnetic fluid bearing of the present invention, since the plate and the shaft are screwed together at the end of the shaft, the plate is fixed to the shaft without bonding, and the contact portion (attachment) between the shaft and the plate is fixed. Regardless of the area, the plate can be fixed at an appropriate angle with respect to the axis. Therefore, it can operate stably and can be manufactured easily.

  The HDD swing arm device of the present invention includes the magnetic fluid bearing described above and a swing arm having a magnetic head for recording information. A swing arm is attached to the outer ring.

  According to the swing arm device of the HDD of the present invention, the magnetic fluid bearing can be stably operated, and the operation of the swing arm is thereby stabilized. Moreover, it can be manufactured easily.

  According to the magnetic fluid bearing of the present invention and the HDD swing arm device provided with the magnetic fluid bearing, it can be stably operated and can be easily manufactured.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a plan view showing a configuration of a magnetic fluid bearing according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 and 2, a magnetic fluid bearing 1 in the present embodiment includes a fixed shaft 2 as a shaft, a sleeve 4 as an outer ring, a flange plate 5 as a plate, and a magnetic fluid 7. ing. A disc-shaped flange plate 5 is fixed to the upper end portion of the fixed shaft 2, and a 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 sleeve 4.

  The fixed shaft 2 has a cylindrical shape with a hollow portion 8, and a female screw is formed on the inner peripheral surface of the hollow portion 8. A magnetic pole forming portion 3 is formed on the outer periphery of the fixed shaft 2. The magnetic pole forming part 3 may be formed integrally with the fixed shaft 2 or may be formed separately.

  A disc-shaped flange plate 5 is fixed to the upper portion of the fixed shaft 2. The flange plate 5 has a projecting portion 9 at a disc-shaped central portion, and a male screw is formed on the outer peripheral surface of the projecting portion 9. The protruding portion 9 of the flange plate 5 and the hollow portion 8 of the fixed shaft 2 are screwed to each other, whereby the flange plate 5 is fixed to the upper end portion of the fixed shaft 2. A cross-shaped groove 15 for inserting a tool is formed on the upper surface of the flange plate 5. 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 flange plate 5 and the flange portion 6 extends in a direction perpendicular to the fixed shaft 2 (lateral direction in FIG. 2), and a recess 11 is formed by the flange plate 5, the fixed shaft 2, and the flange portion 6. Has been.

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

  3A is an enlarged view of a portion A in FIG. 2, and FIG. 3B is an enlarged view of a portion B in FIG. 3A and 3B, the lower surface 5a of the flange plate 5 and the axial upper end surface 4a of the convex portion 12 of the 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 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 sleeve 4 are opposed to each other. A magnetic fluid 7 is injected into the gap between the outer peripheral surface 3b of the fixed shaft 2 and the inner peripheral surface 4b of the sleeve 4, and the fixed shaft 2 and the sleeve 4 constitute a radial sliding bearing which is a magnetic fluid bearing. . In addition, the magnetic fluid 7 is also injected into the gap between the lower surface 5a of the flange plate 5 and the axial upper end surface 4a of the sleeve 4, and the gap between the upper surface 6a of the flange portion 6 and the axial lower end surface 4c of the sleeve 4. Each of the sleeve 4 and the flange plate 5 and the sleeve 4 and the flange portion 6 constitutes a thrust slide bearing by boundary lubrication.

  Each of the fixed shaft 2, the sleeve 4, and the flange 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. However, when the fixed shaft 2 and the magnetic pole forming portion 3 are made of the same material, the fixed shaft 2 is made of a magnetic material.

  The magnetic fluid 7 is made of, for example, a liquid in which magnetic particles are dispersed in a colloidal form. Further, for example, a material such as fatty acid, alcohol, aliphatic amide, ester, sulfurized fat or oil, or a derivative of these materials (hereinafter sometimes referred to as a lubricating material) is 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.

  4 is a diagram showing the magnetic pole distribution of the magnetic pole forming portion in the cross section taken along the line IV-IV in FIG. 2, and FIG. 5 is a diagram showing the magnetic pole distribution in the developed view of the magnetic pole forming portion. 4 and 5, a plurality of magnetic poles are formed in the magnetic pole forming portion 3 on the outer peripheral surface of the fixed shaft 2 so that the plurality of magnetic poles are arranged in the circumferential direction (lateral direction in FIG. 5). 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. 5).

  The magnetic pole forming portion 3 is free to be magnetized, and may be in a magnetized state as shown in FIG. 6 or 7 in addition to the magnetized state shown in FIGS. 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. 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. 7, 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.

  The magnetic fluid bearing 1 in the present embodiment includes a cylindrical fixed shaft 2, a sleeve 4 that is disposed on the outer periphery of the fixed shaft 2 and has an inner peripheral surface 4 b that faces the outer peripheral surface 3 b of the fixed shaft 2, A flange plate 5 having a lower surface 5a screwed to the fixed shaft 2 at the end of the shaft 2 and facing the axial upper end surface 4a of the sleeve 4, an outer peripheral surface 3b of the fixed shaft 2, and an inner peripheral surface 4b of the sleeve 4 And a magnetic fluid 7 injected into the gap between the axial upper end surface 4a of the sleeve 4 and the lower surface 5a of the flange plate 5. A plurality of magnetic poles are formed on the outer peripheral surface 3 b of the fixed shaft 2.

  The magnetic fluid bearing 1 according to the present embodiment is manufactured by inserting a sleeve 4 into the fixed shaft 2, inserting a tool into the groove 15, rotating the tool, and screwing the flange plate 5 to the fixed shaft 2. Is done. As a result, the flange plate 5 is fixed to the fixed shaft 2 without bonding, and the flange plate 5 is appropriately attached to the fixed shaft 2 regardless of the area of the contact portion (attachment) between the fixed shaft 2 and the flange plate 5. Can be fixed at any angle. Therefore, it is possible to operate stably. Further, assemblability and cost advantages can be obtained, and it can be easily manufactured.

  In the present embodiment, a configuration in which the magnetic pole forming portion 3 is formed on the outer peripheral surface of the fixed shaft 2 has been described. Instead of such a configuration, a magnetic pole forming portion (a plurality of magnetic pole forming portions) is provided on the inner peripheral surface 4b of the sleeve 4. Magnetic poles) may be formed. Further, the configuration in which the flange portion 6 is formed integrally with the fixed shaft 2 has been shown. However, like the flange plate 5, the flange portion 6 formed separately from the fixed shaft 2 is screwed to the fixed shaft. 2 may be fixed.

(Embodiment 2)
FIG. 8 is a plan view showing the configuration of the magnetic fluid bearing according to the second embodiment of the present invention. 9 is a cross-sectional view taken along line IX-IX in FIG. With reference to FIGS. 8 and 9, in the magnetic fluid bearing 1 of the present embodiment, a protrusion 13 is formed so as to close the upper portion of the hollow portion 8 at the center of the fixed shaft 2. A groove 16 is formed between the fixed shaft 2 and the fixed shaft 2. A male screw is formed on the outer peripheral surface of the protrusion 13. Further, the flange plate 5 has an annular protrusion 14 at the center of the disk shape, and an internal thread is formed on the inner peripheral surface of the protrusion 14. A hexagonal groove 15 (FIG. 8) for inserting a tool is formed on the upper surface of the flange plate 5. A protrusion 14 is inserted into the groove 16, and the flange plate 5 and the fixed shaft 2 are screwed together.

  In addition, since the structure of the magnetic fluid bearing 1 other than this is the same as that of the magnetic fluid bearing in Embodiment 1, the same code | symbol is attached | subjected to the same member and the description is not repeated.

  The magnetic fluid bearing 1 according to the present embodiment is manufactured by inserting a sleeve 4 into the fixed shaft 2, inserting a tool into the groove 15, rotating the tool, and screwing the flange plate 5 to the fixed shaft 2. Is done. Thereby, the substantially same effect as the magnetic fluid bearing of Embodiment 1 can be acquired.

(Embodiment 3)
FIG. 10 is a cross-sectional view showing the configuration of the HDD swing arm device according to the third embodiment of the present invention. Referring to FIG. 10, swing arm device 21 includes magnetic fluid bearing 1 and 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 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 sleeve 4 of the magnetic fluid bearing 1. Thereby, the swing arm 22 can swing around the fixed shaft 2 (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 magnetic force is generated between the rotor 26a and the stator 26b by an electric current flowing through the rotor 26a, and the swing arm 22 is swung using the magnetic force as a power to move 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. Since the magnetic fluid bearing 1 has a property that the magnetic fluid is held between the fixed shaft and the sleeve by magnetic force, the magnetic fluid bearing 1 is suitable as a support structure of a swing arm device of an HDD swing arm device.

  According to the swing arm device 21 of the HDD in the present embodiment, the magnetic fluid bearing 1 can be stably operated, and the operation of the swing arm 22 is thereby stabilized. Moreover, it can be manufactured easily.

  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 ferrofluid bearing of the present invention is suitable as a fulcrum bearing for a swing arm of an HDD whose progress in miniaturization is remarkable.

It is a top view which shows the structure of the magnetic fluid bearing in Embodiment 1 of this invention. It is sectional drawing along the II-II line of FIG. (A) is the A section enlarged view of FIG. 2, (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 IV-IV 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 a top view which shows the structure of the magnetic fluid bearing in Embodiment 2 of this invention. It is sectional drawing along the IX-IX line of FIG. 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

  1,101 magnetic fluid bearing, 2,102 fixed shaft, 3,103 magnetic pole forming portion, 3b outer peripheral surface of fixed shaft, 4,104 sleeve, 4a upper end surface in axial direction of sleeve, 4b inner peripheral surface of sleeve, 4c Lower end surface in the axial direction, 5,105 flange plate, 5a lower surface of flange plate, 6,106 flange portion, 6a upper surface of flange portion, 7,107 magnetic fluid, 8,108 hollow portion, 9,13,14 projection portion, 11 , 111 Concavity, 12, 112 Convex, 15, 16 Groove, 21 Swing arm device, 22 Swing arm, 23 Base, 24 Magnetic head, 25 Magnetic disk, 26 Head positioning mechanism, 26a Rotor, 26b Stator.

Claims (2)

A cylindrical shaft;
An outer ring disposed on the outer periphery of the shaft and having an inner peripheral surface facing the outer peripheral surface of the shaft;
A plate having a main surface that is threadedly engaged with the shaft at the end of the shaft and that faces the axial end surface of the outer ring;
A magnetic fluid injected into the gap between the outer peripheral surface of the shaft and the inner peripheral surface of the outer ring and the gap between the axial end surface of the outer ring and the main surface of the plate;
A magnetic fluid bearing, wherein a plurality of magnetic poles are formed on an outer peripheral surface of the shaft or an inner peripheral surface of the outer ring. A ferrofluid bearing according to claim 1;
A swing arm having a magnetic head for recording information,
A swing arm device for a hard disk, wherein the swing arm is attached to the outer ring.

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