JP2000234617A - Bearing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing structure under a dynamic pressure which can stably support even a short rotary shaft in both radial and thrust directions, and effectively suppress the deflection of the rotary shaft. SOLUTION: A disk-shaped flange 27 is integrally provided in a rotary shaft 18. Between it and a fixed side member receiving the rotary shaft 18, a dynamic pressure bearing is constituted of a thrust bearing part which has the upper surface and the lower surface of the disk-shaped flange orthogonal to an axial line of the rotary shaft 18 as a thrust receiving surface, and of a radial bearing part which has the external peripheral surface of the disk-shaped flange as a radial receiving surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure suitable for a rotary device such as a disk drive motor of a card-type magnetic recording device, in which the axial dimension of a rotary shaft cannot be increased.

[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 outer thickness is only 5.0 mm, and the motor must be incorporated within this dimension, and the axial dimension of the rotating shaft is only about 2.5 mm. In addition, this type of motor is required to have smooth rotation and low rotation resistance, stable rotation without shaft deflection, and durability.

[0003] Further, as data handling accuracy on a recording medium becomes higher, higher rotational accuracy is required for a motor for driving a disk. By the way
A motor used in a card-type magnetic recording device conforming to the PCMCIA standard type 2 and incorporating a rolling bearing such as a ball bearing has a diameter of 0.3 to 0.3 mm during rotation.
Although there is a run-out of the rotating shaft of 8 μm, if this is configured as a dynamic pressure bearing, the run-out of the rotary shaft can be suppressed to 0.01 to 0.05 μm, and the rotation of the disk can be further stabilized. it can. Furthermore, it is often difficult to incorporate a rolling bearing such as a ball bearing in terms of dimensions, and in the case of a rolling bearing, small oil particles may be scattered during rotation and contaminate the disk. For this reason, the use of a dynamic pressure bearing using a magnetic fluid (a mixture of fine powder magnets in a fluid such as oil) as a working fluid has been proposed as a bearing structure of this type of motor for driving a disk. The dynamic pressure bearing raises and supports the rotating shaft by increasing the pressure in the bearing space accompanying the rotation of the shaft, so the frictional resistance of the rotating shaft is small, durable, the starting characteristics of the motor and the rotation as described above Good accuracy. Further, the magnetic fluid as the working fluid is sealed in the bearing space with permanent magnets or electromagnets, and oil particles are less likely to be scattered during operation. Some dynamic pressure bearings use liquids or gases other than magnetic fluids, and are not limited to card-type magnetic recording devices and can be used at appropriate locations. By the way, a general dynamic pressure bearing is provided with a thrust bearing portion which receives a force along an axial direction of a rotating shaft and a radial bearing portion which receives a force along a circumferential direction, and the runout of the rotating shaft is also increased. The radial bearings are arranged at two positions in the axial direction to prevent the occurrence of such problems (for example, Japanese Utility Model Laid-Open No. 64-18625 and Japanese Patent Laid-Open No. Hei 10-96421). In addition, since the two support points are close to each other, it is difficult to sufficiently prevent the shaft from oscillating.

[0004]

According to the present invention, even if the rotating shaft is short, it is possible to stably support both the radial direction and the thrust direction, and it is possible to effectively suppress the runout of the rotating shaft. Another object is to provide a bearing structure using dynamic pressure.

[0005]

A bearing structure by dynamic pressure is constituted by a shaft body and a fixed side member which supports the shaft body. The fluid filled in the dynamic pressure space to obtain the dynamic pressure may be a liquid or a gas. A disk-shaped flange is integrally provided on the rotating shaft to form a shaft, and a substantial dynamic pressure bearing is formed between this portion and the fixed-side member. That is, the upper and lower surfaces of the disk-shaped flange orthogonal to the axis of the rotary shaft constitute the thrust bearing surface, and the radial bearing portion has the radially outer surface of the disk-shaped flange.
With this configuration, the rotating shaft is substantially supported by a disc-shaped flange, and since the disc-shaped flange can have relatively large upper and lower surfaces regardless of the length of the rotating shaft, Deflection of the rotating shaft can be effectively suppressed. That is, if the upper and lower surfaces of the disc-shaped flange spreading in the direction perpendicular to the axial direction of the rotating shaft are large, the rotating shaft can be stably supported in the thrust direction, and the rotating shaft center of the force acting on the flange peripheral edge portion , The vibration of the rotary shaft is suppressed by a small force, and the support of the rotary shaft is stabilized even in the radial direction. In addition, as the deflection of the rotating shaft is effectively suppressed on the upper and lower surfaces of the disk-shaped flange, the radial supporting surface is small and there is no need to provide a supporting portion at two places. Can be.

The dynamic pressure bearing may use a magnetic fluid as a working fluid. Then, in order to enclose the magnetic fluid in the dynamic pressure space by magnetic force, a magnetic circuit is formed from the outer peripheral surface of the disk-shaped flange through the upper and lower surfaces using a donut-shaped magnet member magnetized in the thickness direction. . For this reason,
The rotating shaft is made of a magnetic material, while the disc-shaped flange is made of a non-magnetic material, and the yoke is attached to the upper and lower surfaces of a donut-shaped magnet member. This structure is used in card-type magnetic recording devices because the working fluid in the dynamic pressure space is strongly sealed by magnetic force and centrifugal force, so there is almost no generation of oil particles and the rotating shaft can be shortened. It is suitable as a bearing structure for supporting a rotor shaft of a thin motor having a small thickness.

In some cases, the thickness of the magnet member is made larger than the thickness of the disc-shaped flange by the upper and lower dynamic pressure spaces. According to this configuration, an appropriate dynamic pressure space can be formed between the upper and lower surfaces of the disk-shaped flange by overlapping the yoke body on the magnet member, even if the upper and lower yoke bodies are simply punched from a flat plate material. it can. There is little processing for the upper and lower yoke bodies, the structure can be simplified, and the cost of the product can be reduced. The inner peripheral surface of the magnet member may be a surface of the radial bearing that directly contacts the magnetic fluid. By using the magnet member as a direct member facing the shaft, the number of parts and the number of assembling steps can be reduced. Further, a magnetic circuit formed between the magnet member and the rotating shaft is shortened, and the magnetic force of the magnet member can be effectively used. The dynamic pressure bearing is often provided with a dynamic pressure groove on a surface opposed to the dynamic pressure space, but in this case, a dynamic pressure groove is formed on the disk-shaped flange side to avoid processing into a hard magnet member. .

On the other hand, a ring member made of a nonmagnetic material such as synthetic resin or brass may be provided on the inner peripheral surface of the magnet member, and the inner peripheral surface of the ring member may be a surface in contact with the magnetic fluid in the radial bearing portion. With this configuration, in the radial bearing portion, the dynamic pressure groove can be easily formed also on the fixed portion side. By processing the inner peripheral surface of the ring member precisely instead of using a hard magnet member, the dynamic pressure space can be formed more precisely and simply. If the area of the thrust bearing is larger than the area of the radial bearing, the function of suppressing the rotation of the rotating shaft may be further enhanced.

[0009]

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, a rectangular card-type magnetic recording device 1
When the card-type magnetic recording device 1 is mounted on an information device, the thickness direction is defined as [upper] or [lower]. The side on which the recording medium cartridge is mounted
And 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 apparatus 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. 3). 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.
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 case body 4 is open so that the disk cassette 14 can be detached. This opening is closed by a shutter 15 which is attached to the rear end of the lower cover 6 so as to be able to be turned upside down. The disk cassette 14 has a disk-type recording medium 16 contained therein so as to be rotatable. When the disk-type recording medium 16 is mounted on the card-type magnetic recording apparatus 1, the shutter of the cassette is opened and the internal disk recording medium 16 is moved to the head body 9. Of the head.

The disk drive motor 2 is for driving and rotating the disk recording medium 16, and has a rotor 19 having a plate-shaped stator 17 having a thickness of 2.5 mm and a rotating shaft 18.
And a bearing 20 (FIG. 3), which is mounted in a motor mounting recess 21 (FIG. 4) on the upper surface of the frame plate 8. The stator 17 has a structure in which a stator coil 24 is radially arranged on a magnetic ring-shaped frame 23 having an opening 22 for accommodating the rotor 19 in the center.
Is provided with a rotor magnet 25 facing the stator coil 24 on the lower surface of the peripheral portion 19a. In this embodiment, the rotor 19 has a peripheral portion 19a made of stainless steel (SUS416) and a central portion 19b made of non-magnetic stainless steel (SUS303).

The shaft 18 has a structure in which a brass (non-magnetic material) disk-shaped flange 27 is integrally mounted on a magnetic material rotating shaft 26. Herringbones are provided on the upper and lower surfaces and the outer peripheral surface of the disk-shaped flange 27. A so-called dynamic pressure groove 28 is formed (FIGS. 5 and 6). The bearing 20 includes a donut-shaped magnet member 29, an upper yoke body 30, and a lower yoke body 31.
These are fixed to the motor shaft mounting hole 32 (FIG. 4) of the frame plate 8 at the lower part, and are fixed members with respect to the shaft body 18. The magnet member 29 is formed of a rare earth sintered magnet. The magnet member 29 is magnetized in the thickness direction, and the inner surface of the donut shape has a disk-shaped flange 27 on the shaft body 18.
Is precisely formed by polishing or the like so as to have a diameter 4 to 5 μm larger than the outer shape of the disk-shaped flange 27, and is accurately formed by polishing or the like so that the thickness dimension is 4 to 5 μm larger than the thickness dimension of the disc-shaped flange 27. I have. Upper yoke body 3
Numeral 0 is formed by punching out a magnetic plate material into a ring shape, and is attached to the upper surface of the magnet member 29 so that its inner edge projects inward from the inner edge of the magnet member 29.
The lower yoke body 31 is attached to the lower surface of the magnet member 29 in a disk shape.

The shaft 18 and the bearing 20 are connected to a lower yoke 31
After fixing the ring-shaped magnet member 29 to the
The shaft body 18 is placed from above, and the upper yoke body 30 is mounted from above, and this is attached and fixed to the upper surface of the magnet member 29 to assemble. In the assembled state, the inner edge of the upper yoke body 30 extends to the upper surface of the disc-shaped flange 27. Since the lower yoke body 31 is a disk and extends to the inner region of the ring-shaped magnet member 29, it can be said that it extends to the lower surface of the disk-shaped flange 27. Further, the upper and lower surfaces of the disc-shaped flange 27 and the upper and lower yoke bodies 30,
31 and between the outer peripheral surface of the disc-shaped flange 27 and the inner peripheral surface of the magnet member 29, a dynamic pressure space having a spacing of 4 to 5 μm is formed.

In this state, the magnetic fluid is press-fitted from the upper portion of the bearing 20 through the gap between the rotating shaft 26 and the inner peripheral surface of the upper yoke 30, and is simultaneously sucked from the small hole provided in the lower yoke 31. The magnetic fluid is filled in the dynamic pressure space. After filling, the small holes used for suction are closed with solder or the like, and the rotor 19 is attached to the rotating shaft 26 of the shaft 18. The central portion 19b of the rotor 19 has an outer diameter that completely covers the disc-shaped flange 27 of the shaft 18. The magnetic lines of force of the donut-shaped magnet member 29 magnetized in the thickness direction are cross-sectionally formed by the upper yoke 30, the rotating shaft 26, and the lower yoke 31.
A magnetic circuit is formed that wraps the dynamic pressure space between the disk-shaped flange 27 and the bearing 20 through the path (FIG. 7). As a result, the thrust bearing portion 34 between the upper and lower surfaces of the disc-shaped flange 27 and the upper and lower yoke bodies 30 and 31 that seals the magnetic fluid by magnetic force becomes the outer peripheral surface of the disc-shaped flange 27 and the inner peripheral surface of the magnet member 29. A radial bearing 34 in which the magnetic fluid is sealed by magnetic force forms a dynamic pressure bearing.

When electric power is supplied to the stator 17, the rotor 19 starts rotating and reaches a predetermined rotation speed (2900 to 300).
At 0 rpm), the fluid pressure in the dynamic pressure space increases, and the shaft 18 rotates while floating with respect to the bearing 20. Even if the dynamic pressure increases or the air pressure in the external space decreases, the magnetic fluid is sealed in the dynamic pressure space by magnetic force, and no oil particles are generated in a normal state. Further, since the thrust is supported by the upper and lower surfaces of the disk-shaped flange 27 having a large area, the shaft 18 is efficiently restrained from swaying, so that the shaft 18 has a small axial dimension despite its small size. , Rotor 1
9 rotates stably. Further, the inner peripheral surface of the magnet member 29 directly contacts the magnetic fluid, that is, the magnet member 29
Since there is no other member between the shaft member 18 and
The magnetic circuit formed between the magnet member 29 and the rotating shaft 26 is short, and the magnetic force of the magnet member 29 can be used effectively.

FIG. 8 shows a second embodiment, in which a ring member 33 of a nonmagnetic material having the same vertical dimension as the magnet member 29 is attached to the inner peripheral surface of the ring-shaped magnet member 29. A dynamic pressure space is formed between the inner peripheral surface and the outer peripheral surface of the disk-shaped flange 27, and a radial bearing portion 35 using a magnetic fluid is formed. The dynamic pressure groove 28 can be formed on the inner peripheral surface of the ring member 33 on the bearing 20 side by adopting a soft material for the ring member 33. FIG. 9 shows a third embodiment, in which the thickness of the ring-shaped magnet member 29 is smaller than the thickness of the disc-shaped flange 27. The thickness of the upper and lower yoke members 30 and 31 is increased accordingly, and
Is thinned by cutting, and a dynamic pressure space is formed by this cutting. According to this configuration, in order to form an accurate dynamic pressure space, the hard magnet member 29 is used as a material.
Upper and lower yoke bodies 3 that are relatively easy to process rather than polishing
By cutting 0 and 31, a dynamic pressure space can be easily obtained.

Although the embodiment has been described above, the rotating shaft 26 is not limited to the motor shaft of the card-type magnetic recording device 1,
Further, the working fluid that fills the dynamic pressure space is not limited to the magnetic fluid. Examples of the magnetic material include SUS430 and mild steel, and examples of the nonmagnetic material include SUS330, synthetic resin, brass, and phosphor bronze. The dynamic pressure groove 28 in the thrust bearing portion 34 may be formed on the surface of the upper and lower yoke members 30 and 31 facing the disk-shaped flange 27.

[0018]

According to the first aspect of the present invention, in the dynamic pressure bearing, the disk-shaped flange having a relatively large area serves as a thrust load receiving surface and suppresses the rotation of the rotary shaft. It is not necessary to separate the portion receiving the load in the axial direction of the rotating shaft, and even when the axial size of the rotating shaft is small, the shaft can be rotated with less vibration and stable rotation can be obtained. In addition, since the upper and lower surfaces of the disk-shaped flange are used as thrust receiving surfaces and the outer peripheral surface of the disk-shaped flange is used as a radial bearing surface, there is no need to separately provide a thrust bearing member and a radial bearing member on the rotating shaft. The structure can be simplified and the axial dimension of the rotating shaft can be reduced.

According to the second aspect of the present invention, in the dynamic pressure bearing, even when the axial dimension of the rotary shaft is small, the shaft can be rotated with a small amount of runout and stable rotation can be obtained. Since the fluid is sealed by magnetic force,
Oil particles are hardly scattered, and the bearing structure is excellent as a bearing for a disk drive motor of a device having a small thickness such as a card-type magnetic recording device. Claim 3,
According to the configuration described in No. 4, the dynamic pressure bearing made of a magnetic fluid has a simple structure, and the cost of each component is reduced, so that the cost of the product can be reduced. According to the configuration of the fifth aspect, the structure of the dynamic pressure bearing using the magnetic fluid is simple, and the magnetic circuit between the magnet member and the rotating shaft on which the disk-shaped flange is mounted is short, so that the magnetic circuit is wrapped in this circuit. The ability to seal the magnetic fluid in the thrust bearing and the radial bearing with magnetic force is high.

According to the sixth aspect of the present invention, the ring member is subjected to processing that is originally performed on the ring member, for example, by forming a dynamic pressure groove on the inner peripheral surface of the ring member. Processing can be avoided and product costs can be reduced.
According to the configuration described in claim 7, it is possible to more effectively suppress the rotation of the rotating shaft. According to the configuration described in claim 8, the working fluid pressure in the dynamic pressure space can be increased, and the bearing structure using the dynamic pressure can be made reliable.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a bearing portion of a disk drive motor (first embodiment).

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 a plan view of a shaft body.

FIG. 6 is a side view of a shaft body.

FIG. 7 is an enlarged sectional view showing a bearing portion.

FIG. 8 is an enlarged sectional view showing a bearing portion (second embodiment).

FIG. 9 is an enlarged cross-sectional view of a bearing (third embodiment).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Card-type magnetic recording device 2 Disk drive motor 3 Bearing structure 4 Case frame 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 Shaped recording medium 17 Stator rotating part 18 Shaft 19 Rotor 20 Bearing 21 Motor mounting recess 22 Opening 23 Ring frame 24 Stator coil 25 Rotor magnet 26 Rotating shaft 27 Disk-shaped flange 28 Dynamic pressure groove 29 Magnet member 30 Upper yoke 31 Lower yoke body 32 Motor mounting hole 33 Ring member 34 Thrust bearing part 35 Radial bearing part

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Ono 6-11-12 Honcho, Tanashi-shi, Tokyo Citizen Watch Co., Ltd. Tanashi Works F-term (reference) 3J011 AA04 AA07 AA10 AA11 AA20 BA08 CA02 DA01 JA02 JA03 KA04 LA05 MA02 MA12 PA02 QA01 RA04 SB20 SC01

Claims (8)

[Claims] A disk-shaped flange (27) whose axis is orthogonal to a rotation surface is integrally provided on a rotating shaft (26) to form a shaft (18).
7 is provided with a thrust bearing portion 34 having an upper surface and a lower surface as a thrust receiving surface, and a radial bearing portion 35 having an outer peripheral surface of the disc-shaped flange 27 as a radial receiving surface, and these constitute a dynamic pressure bearing. Characteristic bearing structure. 2. A structure for forming a dynamic pressure bearing between a shaft body 18 and a fixed-side member receiving the shaft body 18, wherein the shaft body 18 comprises:
A non-magnetic disc-shaped flange 27 whose axis is orthogonal to the rotating surface is integrally attached to a rotating shaft 26 made of a magnetic material, and the fixed side member is a donut-shaped magnet member 29 magnetized in the thickness direction. An upper yoke body 30 and a lower yoke body 31 are attached to the upper and lower surfaces of the magnet member 29 and extend to the upper and lower surfaces of the disk-shaped flange 27, respectively. A magnetic fluid is sealed by magnetic force in a dynamic pressure space between the bearings 31 to form a thrust bearing portion 34, and the outer peripheral surface of the disc-shaped flange 27 and the magnet member 29
A bearing structure characterized in that a magnetic fluid is sealed by magnetic force in a dynamic pressure space between inner peripheral surfaces of the radial bearings to form a radial bearing portion 35, and a dynamic pressure bearing is constituted by these. 3. The bearing structure according to claim 2, wherein the thickness of the magnet member 29 is made larger than the thickness of the disk-shaped flange 27 by an amount corresponding to a dynamic pressure space above and below. 4. The upper and lower yoke members 30, 31 have a substantially uniform thickness in a region covering the magnet member 29 and the disk-shaped flange 27.
The bearing structure according to the above. 5. An inner peripheral surface of the magnet member 29 is a surface to which a magnetic fluid is in direct contact.
The bearing structure according to any one of the above. 6. The magnetic member according to claim 2, wherein a ring member made of a non-magnetic material is provided on an inner peripheral surface of the magnet member, and the inner peripheral surface is used as a magnetic fluid contact surface. The bearing structure as described. 7. The bearing structure according to claim 1, wherein an area of the thrust bearing portion is larger than an area of the radial bearing portion. 8. The bearing structure according to claim 1, wherein a groove 28 for dynamic pressure is formed on an outer peripheral surface of the disc-shaped flange 27.