JP2000257632A - Bearing structure of disc driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing structure which can stably support a short rotor shaft by filling a dynamic pressure space between a the rotor shaft and a bearing member with magnetic fluid, and integrally fitting an annular flange made of a non-magnetic material. SOLUTION: A rotor shaft 20 is a magnetic body, an annular flange 27 is formed of non-magnetic material, and an annular flange 27 is integrally fixed to the rotor shaft 20. A bearing member 19 includes an annular magnet 29, an upper yoke body 30 and a lower yoke body 31 to rotatably support the rotor shaft 20. The annular magnet 29 is formed of rare earth sintered magnet, magnetized in the direction of thickness, and the inside surface thereof has a diameter larger than that of the annular flange 27 by 4-5 μm and a thickness thereof is formed larger to the same extent. The upper yoke body 30 is formed by punching a plate piece made of magnetic material like a ring, and installed on the upper surface of the annular magnet 29, the inner edge being bulged inward over the inner edge of the annular magnet 29, and the lower yoke body 31 is disc-like and installed on the lower surface of the annular magnet 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing suitable for a motor, such as a disk drive motor of a card-type magnetic recording apparatus, which has a disk shape as a whole and cannot have a large axial dimension of a rotor shaft. Regarding the structure.

[0002]

2. Description of the Related Art For example, a card-type magnetic recording apparatus using a disk as a recording medium requires a motor for rotating the disk. The profile thickness is only 5.0 mm and the motor must be built into this dimension. Therefore, the motor is thin and disk-shaped as a whole, and the axial dimension of the rotor shaft is only about 2.5 mm. In addition, this type of motor is required to have smooth rotation and low rotation resistance, and to have stable rotation without shaking of the shaft.

[0003] Incorporating a rolling bearing such as a ball bearing is often difficult in dimensions, and in the case of a ball bearing, there is a run-out of the rotating shaft of 0.3 to 0.8 µm in the diameter direction during rotation. In the case of a hydrodynamic bearing using a magnetic fluid (a fine powder magnet mixed with a fluid such as oil) as a working fluid,
Because the shaft is raised and supported by increasing pressure in the bearing space accompanying rotation of the shaft, frictional resistance of the rotating shaft is small,
It is durable, and the rotation of the rotating shaft is 0.01 to 0.0
The accuracy is as high as 5 μm, and the motor starting characteristics are good. By the way, a general dynamic pressure bearing is provided separately with a thrust bearing portion that receives a force along the axial direction of the rotating shaft and a radial bearing portion that receives a force along the circumferential direction.
Further, in order to prevent the rotation shaft from swinging, radial bearing portions are arranged at two positions in the axial direction (for example, see Japanese Utility Model Application Laid-Open No.
18625, JP-A-10-96421),
If the rotating shaft is short, it is difficult to manufacture and the cost is high. In addition, since the two supporting points are close to each other, it is difficult to sufficiently prevent the shaft from swinging.

[0004]

According to the present invention, even if the rotor shaft is short, the rotor can be stably supported in both the radial and thrust directions, and the swing of the rotor shaft can be effectively suppressed. An object is to provide a bearing structure for a disk drive motor.

[0005]

A rotor structure integrally provided with an annular flange and a bearing member for supporting the rotor shaft constitute a bearing structure by dynamic pressure. The fluid filling the dynamic pressure space between the rotor shaft and the bearing member is a magnetic fluid. The rotor shaft is made of a magnetic material, and an annular flange made of a non-magnetic material is integrally attached thereto. A substantial dynamic pressure bearing is formed between the annular flange and the bearing member. That is, the thrust load and the radial load of the rotor shaft are supported by the magnetic fluid filled in the dynamic pressure space between the annular flange and the bearing member surrounding the annular flange.

In this structure, the rotor shaft is substantially supported by the annular flange, and the upper and lower surfaces of the annular flange can have relatively large diameters regardless of the length of the rotor shaft. And if the diameter of the annular flange that spreads in the direction perpendicular to the axial direction of the rotor shaft is large and the upper and lower surfaces are large, the rotor shaft can be stably supported in the thrust direction and the rotor shaft can be shaken with a slight force. Can be suppressed. Therefore, the support is stable even in the radial direction. Further, as a result of the shaft swing being effectively suppressed on the upper and lower surfaces of the annular flange, the radial support surface is small, and there is no need to provide two support portions. As a result, the rotor shaft can be shortened.

The dynamic pressure bearing uses a magnetic fluid as a working fluid. In order to keep the magnetic fluid in a dynamic pressure space by magnetic force, a magnet (hereinafter referred to as an annular magnet) magnetized in the thickness direction and arranged in an annular shape. Is used. That is, a magnetic circuit surrounding the upper and lower surfaces from the outer peripheral surface of the annular flange is formed.
For this reason, the rotor shaft is made of a magnetic material, and the annular flange is made of a non-magnetic material. On the other hand, yoke bodies are attached to the upper and lower surfaces of the annular magnet to efficiently guide the lines of magnetic force of the annular magnet to the rotor shaft. This configuration strongly encloses the working fluid in the dynamic pressure space with magnetic force and centrifugal force.

The rotor shaft is shortened by attaching a disk member to the rotor shaft and mounting the annular flange of the rotor shaft as close to the disk member as possible. As a result, since the annular magnet and the upper yoke are close to the lower surface of the disk member, the annular magnet and the upper yoke of the disk member correspond to the annular magnet and the upper yoke so that the magnetic circuit extending from the annular magnet to the rotor shaft is not disturbed by the material of the disk member. The central portion is made of a non-magnetic material. However, since it is necessary to form a magnetic circuit for rotation with the stator side at the outer edge portion of the disk member, it is made of a magnetic material.

As the non-magnetic material, there are synthetic resin, brass, non-magnetic stainless steel and the like, and it is preferable that the material has the same thermal expansion as the outer edge portion. If the annular magnet, which is one of the bearing members, is configured so that its thickness is larger than the thickness of the annular flange by the upper and lower dynamic pressure spaces, the upper and lower yoke bodies that are simply punched from a flat plate material are simply superimposed on the annular magnet,
An appropriate dynamic pressure space can be formed between the annular flange. The annular magnet may have an inner peripheral surface that is in direct contact with the magnetic fluid, or a component made of a material such as brass or synthetic resin that easily forms a dynamic pressure groove may be disposed on the inner surface.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
The bearing structure 3 (FIG. 1) of the disk drive motor 2 in the card type magnetic recording device 1 (FIG. 2) will be described.
For convenience of explanation, when the card-type magnetic recording device 1 having a rectangular shape is mounted on an information device, the front end in the insertion direction is set to [front], the rear end is set to [rear], and the thickness direction is set to [ Up〕
[Down] direction. Up, down, left, right, or front and rear indicate a relative positional relationship, and up and down may be front and rear.

The card-type magnetic recording device 1 includes a case body 4 and upper and lower covers 5 and 6, and the case body 4 includes a frame 7 and a frame plate 8 (FIG. 4). The frame 7 and the frame plate 8 are integrated when the synthetic resin frame 7 is molded (outsert molding). On the upper surface of the frame plate 8 of the case body 4, the disk drive motor 2, the head body 9, the eject mechanism 10 and the like are arranged, and on the lower surface side,
The circuit board 12 is attached via the insulating sheet 11. Reference numeral 13 denotes an external connector attached to the front end of the circuit board 12, for attaching the card type magnetic recording device 1 to a slot of another information device for connection. The rear end of the circuit board 12 is open, and the disc cassette 14
Can be attached and detached. This opening is the lower cover 6
The shutter is closed by a shutter 15 attached to the rear end. The shutter 15 can be moved up and down, and is always urged in the rising direction. When the disk cassette 14 is inserted, the shutter 15 falls down inside the case body 4 to open an opening. The disk cassette 14 contains a disk-type recording medium 16 therein so as to be rotatable. When the disk cassette 14 is mounted on the card-type magnetic recording device 1, the disk recording medium 16 faces the head of the head body 9. ing.

The disk drive motor 2 drives and rotates the disk recording medium 16 and has a thickness of 2.5 mm.
, A disk-shaped rotor 17 and a bearing member 19, and the disk-shaped rotor 18 has a disk member 26, a rotor shaft 20, and an annular flange 27 in this embodiment (FIG. 3). 3). The rotor shaft 20 is short, so that the disk drive motor 2 has a generally flat disk shape and is mounted in a motor mounting recess 21 (FIG. 4) on the upper surface of the frame plate 8.

The disk-shaped stator 17 has a structure in which stator coils 24 are radially arranged in a ring-shaped frame 23 made of a magnetic material and provided with an opening 22 for accommodating the disk-shaped rotor 18 in the center. The member 26 is provided with a rotor magnet 25 on the lower surface of the outer periphery to obtain a rotational force in opposition to the stator coil 24. In addition,
In this embodiment, the disk member 26 has a central portion 18a.
Is formed of a non-magnetic stainless steel (SUS303), and the outer edge portion 18b is made of a magnetic stainless steel (SUS41).
6). Reference numeral 28 denotes a ring magnet attached to the upper surface of the disk member 26, which attracts the metal hub of the disk-shaped recording medium 16 when the cartridge 14 is inserted, and transmits a rotational force.

The rotor shaft 20 is made of a magnetic material, the annular flange 27 is made of a non-magnetic material (for example, brass), and the annular flange 27 is integrally fixed to the rotor shaft 20. The bearing member 19 includes an annular magnet 29, an upper yoke body 30, and a lower yoke body 31. These are fixed to a motor shaft mounting hole 32 (FIG. 4) of the frame plate 8, and rotatably support the rotor shaft 20 having the annular flange 27. The ring magnet 29 is formed of a rare earth sintered magnet. The annular magnet 29 is magnetized in the thickness direction, and is accurately formed by polishing or the like so that the inner surface of the annular shape has a diameter larger by 4 to 5 μm than the outer shape of the annular flange 27 of the rotor shaft 20. The annular flange 27 is accurately formed by polishing or the like so as to be larger than the thickness dimension of the annular flange 27 by 4 to 5 μm. The upper yoke body 30 is formed by punching a magnetic plate material into a ring shape.
The inner edge is attached to the upper surface of the annular magnet 29 and the inner edge is the annular magnet 2.
9 is set to protrude inward from the inner edge. The lower yoke body 31 has a disk shape and is attached to the lower surface of the annular magnet 29.

Rotor shaft 20 with annular flange 27
After the ring magnet 29 is fixed to the lower yoke body 31 by bonding, the rotor shaft 20 is placed from above, and the upper yoke body 30 is mounted from above, and this is mounted on the upper surface of the ring magnet 29. (Fig. 5). After the assembly, the inner edge of the upper yoke body 30 extends to the upper surface of the annular flange 27. Dynamic pressure spaces with a spacing of 4 to 5 μm are continuously formed between the upper and lower surfaces of the annular flange 27 and the upper and lower yoke bodies 30 and 31 and between the outer peripheral surface of the annular flange 27 and the inner peripheral surface of the annular magnet 29. Is done. Further, the annular magnet 29 and the upper yoke 30 mounted on the upper surface thereof are mounted as close as possible to the lower surface of the disk member 26 to make the rotor shaft 20 short. The annular magnet 29 and the upper yoke 30 are connected to the central portion 18 of the disc member 26.
Corresponding to a, this portion is made of a non-magnetic material as described above.

In this state, from above the bearing member 19,
At the same time as the magnetic fluid is press-fitted through the gap between the rotor shaft 20 and the inner peripheral surface of the upper yoke 30, the magnetic fluid is filled into the dynamic pressure space by being sucked from a small hole provided in the lower yoke 31 temporarily. After filling, the small holes used for suction are sealed with solder or the like, and the disk member 26 is attached to the rotor shaft 20. As a result, the line of magnetic force of the annular magnet 29 magnetized in the thickness direction is
In the cross section, a magnetic circuit is formed that has the upper yoke 30, the rotor shaft 20, and the lower yoke 31 as paths.
The dynamic pressure space between the annular flange 27 and the bearing member 19 is wrapped inside (FIG. 5). That is, the annular flange 2
7 between the upper and lower surfaces and the upper and lower yoke bodies 30 and 31 constitutes a thrust bearing portion 33 which seals a magnetic fluid by magnetic force, and a space between the outer peripheral surface of the annular flange 27 and the inner peripheral surface side of the annular magnet 29. And a radial bearing portion 34 in which the magnetic fluid is sealed by magnetic force to form a dynamic pressure bearing.

When electric power is supplied to the stator 17, the disk-shaped rotor 18 starts rotating, and the fluid pressure in the dynamic pressure space increases, and the rotor shaft 20 having the annular flange 27 floats with respect to the bearing member 19. Rotate. Since the rotation is performed without contact between the members, the rotation is smooth and the durability is high. In this embodiment, the rotor shaft 2
Numeral 0 indicates that the thrust is supported by the upper and lower surfaces of the annular flange 27 having a large area, and at the same time, the swinging of the rotor shaft 20 is efficiently suppressed. Rotates stably. further,
Disk member 26 close to annular magnet 29 and upper yoke 30
Since the central portion 18a is made of a non-magnetic material, the magnetic circuit surrounding the dynamic pressure space is not disturbed on the lower surface side of the disk member 26, and the magnetic force of the annular magnet 29 is used for the dynamic pressure bearing. Can be used effectively.

The central portion 18a of the disk member 26 may be made of a non-magnetic material such as synthetic resin or brass with respect to the magnetic material of the outer edge portion 18b. However, in consideration of the trouble such as the need to separately perform the surface treatment and the measures for the displacement of the joint due to the difference in thermal expansion, it is preferable to use stainless steel that is the same kind of material but is magnetic and non-magnetic. Thrust bearing 3
A dynamic pressure groove called a herringbone is formed on the upper and lower surfaces of the annular flange 27, the inner surfaces of the upper and lower yokes 30, 31 or the outer peripheral surface of the annular flange 27 and the inner surface of the annular magnet 29, thereby forming a dynamic pressure. Can be improved. Since the ring magnet 29 is hard as a material, if it is difficult to process the herringbone, a ring of a non-magnetic material is fitted inside the ring magnet 29 and the ring is processed.

Although the embodiment has been described above, the disk type motor is not limited to the one used in the card type magnetic recording apparatus. Other magnetic materials include SUS430,
There are mild steel and the like, and nonmagnetic materials include SUS330, phosphor bronze and the like.

[0020]

The configuration according to the first aspect has the following effects. Since the rotor shaft of the disk-shaped rotor is supported by a dynamic pressure bearing in which a magnetic fluid is sealed by magnetic force, the rotation of the disk-shaped rotor is smooth, and the bearing structure has durability. Since the central part of the disk member in the disk-shaped rotor is made of non-magnetic material, the magnetic circuit that seals the magnetic fluid in the dynamic pressure space is not disturbed even if the ring magnet is close to the disk member, and the magnetic force of the ring magnet is effectively used without waste. And the rotor shaft can be shortened.

According to the second aspect of the present invention, since the outer edge portion of the disk member in the disk-shaped rotor is made of a magnetic material, the efficiency of the magnetic action between the magnet attached to this portion and the stator is improved. , The rotating torque of the disk-shaped rotor is large. According to the third aspect of the present invention, the central portion of the disk member to be made non-magnetic and the outer edge portion to be made of magnetic material are made of the same kind of non-magnetic stainless steel and magnetic stainless steel. The outer edge portion is unlikely to be displaced due to thermal expansion or the like, and the surface treatment or the like performed as necessary can be performed in common, so that work efficiency can be improved and product cost can be reduced.

The structure described in claim 4 has the following effects. The rotor shaft is supported in the thrust direction on the upper and lower surfaces of the annular flange provided on the shaft body, and in the radial direction on the outer peripheral surface, but since the upper and lower surfaces of the annular flange can take a relatively large area. In addition, even if the rotor shaft is short, the shaft swing can be effectively suppressed. Furthermore, since the portion corresponding to the annular magnet and the upper yoke of the disc-shaped rotor is made of a non-magnetic material, the magnetic circuit that seals the magnetic fluid in the dynamic pressure space between the rotor shaft and the bearing member is formed by the disc-shaped rotor. The magnetic force of the annular magnet can be used effectively without being disturbed. Since the upper and lower surfaces of the annular flange are the thrust receiving surfaces, and the outer peripheral surface of the annular flange is the radial bearing surface, there is no need to separately provide a thrust bearing member and a radial bearing member on the rotor shaft, simplifying the bearing structure, In addition, the axial dimension of the rotor shaft can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a bearing portion of a disk drive motor.

FIG. 2 is an exploded perspective view of a card-type magnetic recording device.

FIG. 3 is an exploded perspective view showing a disk drive motor.

FIG. 4 is a perspective view of a frame plate.

FIG. 5 is an enlarged sectional view showing a bearing member;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Card-type magnetic recording device 2 Disk drive motor 3 Bearing structure 4 Case body 5 Upper cover 6 Lower cover 7 Frame 8 Frame plate 9 Head body 10 Ejection mechanism 11 Insulation sheet 12 Circuit board 13 External connector 14 Disk cassette 15 Shutter 16 Disk type Recording medium 17 Stator 18 Disk-shaped rotor 18a Central portion 18b Outer edge portion 19 Bearing member 20 Rotor shaft 21 Motor mounting recess 22 Opening 23 Ring-shaped frame 24 Stator coil 25 Rotor magnet 26 Disk member 27 Ring flange 28 Ring magnet 29 Ring magnet 30 Upper yoke body 31 Lower yoke body 32 Motor mounting hole 33 Thrust bearing part 34 Radial bearing part

Continuation of the front page F term (reference) 3J102 AA01 BA03 CA02 DA02 DA07 GA03 5D109 BB02 BB05 BB18 BB21 BB22 BB31

Claims (4)

[Claims] 1. A rotor comprising: a disk-shaped rotor having a disk member and a rotor shaft made of a magnetic material provided integrally with the disk member; and a bearing member having a magnetized magnet and a yoke body. In a bearing structure in which a magnetic fluid is sealed between an outer peripheral surface of a shaft and a bearing member by a magnetic force of a magnet to form a dynamic pressure bearing, a central portion corresponding to the bearing member of the disk member is formed of a nonmagnetic material, A bearing structure for a disk drive, wherein an outer edge portion of the member is made of a magnetic material. 2. A bearing structure for a disk drive device according to claim 1, wherein a magnet required for rotating a disk-shaped rotor is attached to an outer edge portion of said disk member. 3. The bearing structure for a disk drive according to claim 2, wherein a central portion of the disk member is made of a non-magnetic stainless material, and an outer edge portion thereof is made of a magnetic stainless material. 4. A disk-shaped rotor comprising a disk member and its rotor shaft and a bearing member, wherein the rotor shaft is made of a magnetic material and integrally provided with an annular flange of a non-magnetic material,
The bearing member includes a magnet, an upper yoke body, and a lower yoke body magnetized in a thickness direction and arranged in an annular arrangement, and these yoke bodies are attached to the upper and lower surfaces of the magnet, and the upper and lower surfaces of an annular flange on the rotor shaft are provided. To
A dynamic pressure bearing that seals the magnetic fluid between the upper and lower surfaces and the outer peripheral surface of the annular flange and the bearing member by magnetic force, attaches the rotor shaft to the bearing member, and supports the thrust and radial loads of the rotor shaft by the annular flange. A bearing of a disk drive device, wherein a central portion corresponding to a bearing member of a disk member in a disk-shaped rotor is formed of a non-magnetic material, and an outer edge portion of the disk member is formed of a magnetic material. Construction.