JPH0874841A - Spindle unit, its manufacture and magnetic disc device - Google Patents

Abstract

PURPOSE: To reduce size of a spindle unit such as a magnetic disc, and improve rotational accuracy. CONSTITUTION: In a spindle unit, a sliding bearing 2 is fixed to a rotating hub 1, and a spindle shaft 5 is fitted to a boss 4 of a base plate 3. The sliding bearing 2 is integrated with a radial bearing 2a on its inner peripheral surface, and thrust bearings 2b in its both ends. One end of the sliding bearing 2 is opposed to an end face of the boss 4 formed on the base plate 3, while the other end is opposed to a thrust receiving plate 11 fixed to an end of the spindle shaft 5 In order to set an axial clearance (c), a shim having a specified thickness is inserted between the thrust receiving plate 11 and one end of the sliding bearing 2. The spindle shaft 5 is press-fitted to the hole of the boss 4 until the receiving plate 11, the shim and the end make abutment. The shim is demounted afterward, and the thrust receiving plate 11 is fastened again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle unit for a magnetic disk device, an optical disk device, a laser beam printer or the like, and more particularly to a bearing device for rotating a spindle in a small size and with high accuracy.

[0002]

2. Description of the Related Art With downsizing of computers, downsizing and speeding up of magnetic disk devices and optical disk devices have been advanced.

In the magnetic disk device, the recording density has been increased and the size and capacity have been increased. With this trend, the spindle unit for rotating the magnetic disk, which is a recording medium, at a constant speed has been made compact and have high performance. Is needed.

In the conventional magnetic disk spindle unit, it is generally supported by a ball bearing. When the spindle speed is increased, asynchronous vibration that is not synchronized with the number of revolutions increases in the ball bearing, so that the track pitch cannot be reduced, and there has been a limit to increasing the recording density. For this reason, in the future high-speed rotating spindles, there is no choice but to adopt a sliding bearing method of supporting through an oil film.

However, in the case where the spindle is supported by the slide bearing, it is necessary to perform the positioning in the radial direction and the axial direction and to prevent the vibration, and the corresponding radial and thrust bearings are arranged. . Since it is fluid lubrication, the seal device is an indispensable constituent element for the purpose of maintaining the lubricant in the bearing portion and preventing contamination of the magnetic disk.

Further, the form factor of the small magnetic disk device is regulated, and the size of the magnetic disk determines the length, width and height of the device.

As a spindle adopting a slide bearing system, Japanese Patent Laid-Open No. 61-201916 discloses a rotating shaft and a rotating shaft which are rotatably supported as means for preventing vibration in the radial and axial directions. A cylindrical housing having a gap in the axial direction and the circumferential direction, and a magnetic fluid is sealed in the gap portion. Sealing devices are provided at both ends to prevent leakage of the magnetic fluid to the outside. The bearing force generating member having an arc-shaped dynamic pressure groove facing the surface of the rotary shaft and both end surfaces of the rotary shaft is provided.
A method for suppressing vibration and maintaining stable rotation accuracy is disclosed.

[0008]

In the prior art of the above-mentioned sliding bearing system, the dynamic force effect of the bearing force generating groove enhances the rigidity of the oil film to improve the rotation accuracy. Since it is arranged separately from the bearing part,
Since it is difficult to control the accuracy of proper dimensions, there is a risk that vibration will be amplified if the balance of dynamic pressure is lost. Also,
The dynamic pressure is small in the arcuate groove, which may be insufficient when the spindle is vertically arranged.

[0009] By the way, when the size and speed of rotating equipment is getting smaller, the most important problem in the spindle unit is the dimensional accuracy of the bearing portion. Above all, since the gap size of the thrust bearing part has the greatest effect on the rigidity and loss of the bearing, it is the current situation that the required dimensional accuracy is ensured by relying on the tolerance accuracy of the processing machine. However, as higher machine precision is required, special equipment, labor and technology are required for processing, resulting in high cost and low mass productivity.

Particularly, in the miniaturization of the magnetic disk device, the disk spacing is reduced to several microns to several tens of microns or less as the magnetic disk is thinned, so that the clearance of the thrust bearing may be reduced due to machining or misreading error. If is set excessively, due to shock due to increased vibration or disturbance, mutual magnetic heads set on the upper and lower magnetic disks come into contact with each other and collide with each other to read information,
A write failure occurs, which eventually leads to trouble such as head destruction.

A method has also been proposed in which the bearing portion is processed by molding to improve mass productivity. However, the molding process has poor axial dimensional accuracy, and securing a clearance for the thrust bearing or positioning the spindle is a bottleneck.

Further, with the downsizing and speeding up of the spindle unit, there still remains a problem with the magnetic fluid seal.

An object of the present invention is to provide a spindle unit which overcomes the problems of the prior art and can secure the necessary rotation accuracy or lubrication performance corresponding to miniaturization.

An object of the present invention is to provide a spindle unit capable of ensuring a required dimensional accuracy corresponding to miniaturization and a manufacturing method excellent in mass productivity.

Another object of the present invention is to provide a magnetic disk device which can prevent rotational vibration and contact of a magnetic head, and can be made compact and have a high recording density.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to mount a bearing object, fix a sliding bearing to a rotating hub, and insert a spindle shaft fixed to a base plate into a radial bearing portion of the bearing. In the spindle unit
Thrust bearing portions are integrally formed on both axial end surfaces of the slide bearing, and are arranged to face a boss end surface formed on the base plate and a thrust receiving plate fixed to an end portion of the spindle shaft. This is achieved by providing a dynamic pressure groove in which a lubricating fluid is sealed in the radial bearing portion and / or the thrust bearing portion.

An object of the present invention is to mount a rotating object on which a target object is mounted, a fixed base plate, a double cylinder of the hub, a bearing for using magnetic fluid for lubrication at the innermost side, and a rotor for the inner side. In a spindle unit driven by providing a stator at a position facing the magnet and the rotor magnet of the base plate, a pole piece and a magnet are respectively provided at one end of the inner cylinder of the hub and a predetermined part of the base plate facing the one end. This is achieved by providing a magnetic fluid seal to be arranged and a screw seal on the outer peripheral portion of the inner cylinder of the hub.

An object of the present invention is to provide a spindle unit in which a bearing is mounted and a sliding bearing is fixed to a rotating hub, and a spindle shaft fixed to a base plate is inserted into a radial bearing portion of the bearing. Thrust bearing portions are formed at both ends in the axial direction of the slide bearing,
One end is arranged on a boss end face formed on the base plate and the other end is arranged so as to face a thrust receiving plate fixed to an end of the spindle shaft, and the one end is in contact with the boss end face. In this state, the other end and the thrust receiving plate have a predetermined gap regardless of the axial length of the slide bearing.

An object of the present invention is to provide a method for manufacturing a spindle unit in which a bearing is mounted, a sliding bearing is fixed to a rotating hub, and a spindle shaft fixed to a base plate is inserted into the bearing. The bearing is integrally formed with a radial bearing portion and thrust bearing portions at both ends thereof on its inner peripheral surface, and one end of the formed slide bearing is formed on a boss end surface formed on the base plate, and
The other end is arranged to face a thrust receiving plate fixed to the end of the spindle shaft, and a shim having a predetermined thickness is inserted between the thrust receiving plate and the other end of the slide bearing.
The spindle shaft is press-fitted into the boss hole of the base plate to a position where the receiving plate, the shim and the other end contact each other, and then the shim is removed, and the predetermined distance is provided between the thrust receiving plate and the other end of the slide bearing. This is achieved by setting the gap corresponding to the thickness.

It is an object of the present invention to provide a hub on which a magnetic disk is mounted, a fixed base plate, a double-cylindrical hub having a slide bearing on the innermost side, a rotor magnet on the inner side, and the rotor magnet on the base plate. In the magnetic disk drive driven by providing stators at opposite positions, the slide bearing includes a radial bearing portion on its inner peripheral surface and thrust bearing portions on both ends thereof, and one end portion of the slide bearing portion on the base plate. The formed boss end surface and the other end portion are arranged so as to face a thrust receiving plate fixed to the end portion of the spindle shaft, and the other end portion and the thrust are in contact with the boss end surface. This is achieved by forming a predetermined gap between the receiving plates regardless of the axial length of the slide bearing.

[0021]

In the spindle unit according to the present invention, the radial bearing portion is provided with an arcuate dynamic groove, and the thrust bearing portion is provided with a land taper dynamic pressure groove. The former dynamic pressure action causes the axial center, and the latter dynamic pressure action causes the axial direction. Since the vibration of the rotation is suppressed by ensuring the balance of the above, there is an effect of enhancing the safety by improving the rotation accuracy in the compact structure.

Since the spindle unit according to the present invention is provided with a magnetic fluid seal and a screw seal on the outer peripheral portion thereof to increase the pressure resistance of the latter, leakage of the magnetic fluid can be surely prevented in miniaturization and speeding up. effective.

Since the spindle unit according to the present invention is positioned by inserting the shim having a predetermined thickness corresponding to the gap of the thrust bearing when the spindle is press-fitted,
Since a gap of less than a micron can be set easily and reliably regardless of the shaft length accuracy of the bearing, the spindle unit can be downsized, and the sliding bearing including the radial and thrust bearings can be integrally molded, enabling mass production. There is an effect that can improve.

According to the magnetic disk device of the present invention, since the magnetic disk is carried on the spindle unit of the present invention, the required miniaturization and rotation accuracy can be ensured, and the disk and head can be prevented from being damaged.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 3. FIG. 1 is a vertical sectional view of a spindle unit for a magnetic disk device according to the present invention. FIG. 2 is a perspective view of the sintered slide bearing. FIG. 3 is a cross-sectional view showing a state in which the axial clearance of the plain bearing is set.

In FIG. 1, a slide bearing 2 is mounted on the innermost peripheral side of a double cylindrical hub 1 on which a magnetic disk 20 is mounted. The radial bearing 2a of the slide bearing 2 is
The hub 1 is rotatably supported with a spindle shaft 5 fixed by press fitting in a hole of the boss portion 4 of the base plate 3 and a predetermined gap. A stator 7 is attached to an outer peripheral portion of a housing 6 formed integrally with the base plate 3, and a rotor magnet 8 is fixed to an inner peripheral surface of the hub 1 that faces the hub. The hub 1 is rotationally driven after being configured.

One end of the slide bearing 2 has a base plate 3
The end of the boss 4 and the other end of the boss 4 are opposed to the end of the spindle shaft 5 with a thrust receiving plate 11 fixed with a screw 10 with a slight gap, and the hub 1 is axially positioned. In addition, a thrust bearing 2b that supports the weight of the hub 1 and the magnetic disk 20 is configured.

Normally, the clearance of the radial bearing is 1 to 2 · D /
Within the range of 1000 (D: shaft diameter), and in the case of a thrust bearing, it is set to about several tens of microns or less, which is almost the same as the depth of the groove for dynamic pressure generation.

Further, the radial bearing 2a and the thrust bearing 2
A magnetic fluid 13 is filled as a lubricant in the space where b and the thrust receiving plate 11 are arranged. A cap 30 is provided above the spindle shaft 5 to prevent the magnetic fluid 13 from leaking to the outside, and its outer peripheral portion guides a clamp (not shown) for fastening the magnetic disk 20 to the hub 1. It is fixed.

On the other hand, the pole piece 1 is attached to the lower end of the hub 1.
4, a magnet 15 magnetized in the radial direction is embedded in the base plate 3 facing the pole piece 14 to form a magnetic fluid seal 16. Further, a thread groove is formed on the outer peripheral portion of the pole piece 14 and is arranged with a gap from the inner peripheral portion of the housing 6 to form a screw seal 17.

As a result, the magnetic fluid 13 sealed inside is held by the cap 14, the magnetic fluid seal 16 and the screw seal 17, and is used for both sealing and lubricating action. Since the bearing 2 is fixed to the inner peripheral portion of the hub 1 forming the thread groove by press fitting, the thickness of the bearing 2 is formed to be equal to or thinner than that of the hub 1 to prevent deformation due to press fitting.

A flow passage 18 is formed in the spindle shaft 5 in the axial direction, and is communicated with an oil chamber 21 provided opposite to the inner peripheral surface of the radial bearing 2a via an introduction passage 19 provided in the radial direction. ing.

FIG. 2 shows a perspective view of the slide bearing 2. The slide bearing 2 is made of a sintered powder alloy or an inexpensive plastic-based material, is formed into a cylindrical shape by a mold, and has dynamic pressure grooves on its inner peripheral surface and both end surfaces that exert a dynamic pressure action by rotation. The radial bearing 2a and the thrust bearing 2b are integrally formed by molding. The dynamic pressure groove is formed as a three circular arc groove in the radial bearing 2a and a taper land groove in the thrust bearing 2b. These grooves can be easily formed by molding, and give high rigidity to the spindle unit due to its dynamic pressure action.

The radial direction of the slide bearing is finished with high precision by the sizing method, and the dimensional tolerance of the radial bearing 2a can be set to several microns or less. However, it is difficult to obtain the same accuracy in the axial tolerance by only molding, and adjustment of the clearance of the thrust bearing 2b becomes a problem. In this embodiment, by using the positioning shim 12 during assembly,
The gap is set to be constant regardless of the dimensional error in the axial direction.

FIG. 3 is a cross-sectional view showing (a) before press-fitting, (b) after press-fitting, and (c) a completed state for setting the axial gap of the slide bearing.

When assembling the spindle unit, the spindle shaft 5 inserted into the hole of the boss 4 of the base plate 3
The hub 1 to which the bearing 2 is fixed is mounted on the
Is pushed down to a position where the lower end portion of the bearing contacts the crown of the boss 4 of the base plate 3 (press-fitting of the bearing 2).

In this state (a), a shim 12 having a thickness corresponding to the axial gap is inserted between the thrust receiving plate 11 and the upper end surface of the thrust bearing 2b. The material of the shim 12 is preferably steel or plastic that does not deform even when fastened.

Next, while tightening the thrust receiving plate 11 on the upper end surface of the spindle shaft 5 with the screw 10, the receiving plate 11 and the shim 1 are
2. Spindle shaft 5 until thrust bearing 2b is in close contact
Is press-fitted into the hole of the boss 4 of the base plate 3. As a result, the spindle shaft 5 is positioned and fixed to the base plate 3, and the state of (b) is obtained.

After the fixing, the screw 10 is loosened, the shim 12 is removed, and the screw 10 is fastened again, so that a clearance c corresponding to the thickness of the shim 12 is formed between the thrust receiving plate 11 and the thrust bearing 2b (c ) State. The clearance c during assembly is set to a value obtained by adding the upper and lower clearances (c1, c2) of the thrust bearing 2b.

For the positioning of the spindle shaft 5, shims having thicknesses corresponding to a plurality of spindle shaft diameters are prepared in advance, and a shim having a thickness corresponding to a plurality of spindle shaft diameters is selected in advance so that the accuracy range of several microns or less can be set easily and reliably.

If the spindle unit of this embodiment is applied to various types of magnetic disk devices, the gap between the thrust bearings can be properly managed, so that contact or collision between the magnetic disk and the head due to vibration or shock can be prevented. Information lead,
Problems such as defective writing or magnetic head destruction are eliminated.

Further, since the slide bearing can be molded by using a sintered powder alloy or a plastic material and the thrust and radial bearings can be integrated, mass production is possible and positioning can be performed with high dimensional accuracy.

Next, the operation of the magnetic disk spindle unit configured as described above will be described. When the coil of the stator 7 is energized, the rotor magnet 8 receives a rotational force, and the hub 1 and the bearing 2 on which the magnetic disk 20 is mounted rotate. The magnetic fluid 13 is enclosed in the bearing 2 chamber, and an oil film is formed on the sliding surfaces of the radial bearing 2a and the thrust bearing 2b due to the dynamic pressure effect due to the rotation of the bearing 2. The generation state of this oil film will be described with reference to FIGS. 4 and 5. 4 is a plan view of the slide bearing 2, and FIG. 5 is A of FIG.
FIG.

As shown in the drawing, three circular arc grooves 23 are formed in the radial bearing 2a and tapered grooves 24 are formed in the thrust bearing 2b, and these grooves are oil guiding grooves 22a, 22b.
Through the oil chamber 21.

When the bearing 2 rotates as shown by the arrow (R),
Since the circular arc groove 23 formed in the radial bearing 2a becomes a channel that gradually narrows in the rotational direction, the magnetic fluid 13 flowing into this portion is pressurized and an oil film pressure distribution P ₁ corresponding to the number of circular arc grooves is generated. To do. This pressure distribution P ₁ has a peak at 120 ° intervals on the inner circumference, but when the center of the bearing 2 shifts, the pressure in the narrow part of the gap increases and acts to push it back to the center position, so that the balance of the rotation center is balanced. Maintained. Since the magnetic fluid 13 is sequentially supplied from the oil chamber 21 via the oil guide grooves 22a and 22b, the oil film pressure distribution can be stably maintained.

On the other hand, the thrust bearing 2b has a tapered portion 24.
Grooves composed of the land portion 25 and the land portion 25 are formed symmetrically at both ends of the bearing 2. FIG. 6 shows the thrust bearing 2 in rotation.
The dynamic pressure action of b is shown. When stationary, one end surface of the thrust bearing 2b is in contact with the end surface of the boss 4 (FIG. 3 (c)), but it floats with rotation to form an oil film, and both thrust bearings 2b are shown in FIG. 3 (a). Thus, it is stably supported in a balanced manner at the positions of the gaps c1 and c2.

That is, when the bearing 2 further rises, c1 <c
2, the oil film pressure on the upper side becomes large and the bearing 2 is pushed down (state of FIG. 7B). Conversely, when the bearing 2 descends and c2 <c1, the oil film pressure on the lower side becomes large. Then, the bearing 2 is pushed up (state shown in FIG. 7C). Moreover, since the tapered land-shaped groove can generate a high oil film pressure distribution P ₂ with the land portion 25 as the apex, sufficient dynamic pressure can be obtained not only when the bearing 2 is arranged horizontally but also when it is arranged vertically. Can be given.

In this embodiment, as described above, the dynamic pressure grooves formed in the radial bearing portion and the thrust bearing portion improve the rotation accuracy, and the stable rotation can be maintained regardless of the vertical or horizontal posture of the spindle unit. Since the sliding bearing formed by molding the sintered powder alloy has excellent boundary lubrication characteristics, stable rotation is possible also from this aspect.

Next, the seal structure of this embodiment and its operation will be described.

The magnetic fluid 13 sealed inside the present spindle unit is sealed by a cap 30 on one side and the other side by a double sealing device in which a magnetic fluid seal 16 and a screw seal 17 arranged outside thereof are combined. It is configured to be sealed without contact. The seal withstand pressure is configured such that the outer screw seal 17 has a higher pressure.

According to this seal structure, the magnetic fluid 13 at rest is sealed at the end of the hub 1 by the magnetic circuit formed by the pole piece 14 and the magnet 15. On the other hand, centrifugal force acts on the magnetic fluid 13 during rotation, but since it is pushed back inside due to the dynamic pressure effect of the screw seal 17 provided on the outer peripheral portion of the hub 1, it leaks to the outside and contaminates the magnetic disk 20. There is no. For this reason, the magnetic fluid seal 16 is always arranged inside the screw seal 17.

Also, as to the oscillation vibration during transportation of the apparatus, the axial gap is set to a small value of several tens of microns or less as described above, so that the magnetic fluid 13 is prevented from leaking to the outside. it can.

Next, a second embodiment of the present invention will be described.
FIG. 7 is a cross-sectional view showing a state when the axial gap of the spindle unit is set. Comparing with the structure of FIG.
A step portion is formed on the thrust receiving plate 11 ', and the height c of this step is
Is a value corresponding to the axial gap.

That is, at the time of assembly, the flat thrust receiving plate 11 is fastened to the end of the spindle shaft 5, and the spindle shaft 5 is press-fitted until it comes into contact with the end face of the thrust bearing 2b. Position it so that it is flush. After that, thrust receiving plate 1
When 1 is removed and replaced with a stepped thrust receiving plate 11 ′ and is fastened to the end of the spindle shaft 5, a gap of height c of the stepped portion is created, and the same configuration as in the case of FIG. 3 can be obtained.

FIG. 8 is a sectional view of a spindle unit according to the third embodiment of the present invention. The structural difference from the above-described embodiment is that the spindle shaft has a double-support structure in which it is fixed to the motor base at both ends of the upper cover of the device, and the sealing device is arranged at both ends.

That is, a bottomed cylindrical thrust collar 26 is fitted and arranged at one end of the spindle shaft 5. One end of the thrust collar 26 faces the thrust bearing 2b and is provided with a predetermined axial gap. Further, a magnetic fluid seal 27 and a screw seal 28 are arranged in series in the axial direction on the outer diameter portion of the thrust color 26, and both are fixed to the hub 1.

Here, the magnetic fluid seal 27 and the magnetic fluid seal 16 arranged at the other end have different mounting positions and seal shapes, and are therefore constructed to balance the pressure resistance of both seals. Also, the screw seal 28 is the screw seal 17.
Although the seal diameter is different, the balance can be easily achieved by changing the gap or width of the seal part.

In the spindle unit configured as described above, the axial gap of the thrust bearing 2b is set by setting the shim 12 having a thickness corresponding to a predetermined gap, the thrust bearing 2b and the thrust collar 26 as shown in FIG. And the thrust collar 26 is fastened to the end of the spindle shaft 5, and the same procedure as described above is performed. Further, instead of the shim 12, a stepped thrust receiving plate 11 ′ may be used.

As described above, also in the spindle unit having the both-end support structure, the same effect as in the case of the first embodiment can be obtained. It should be noted that, in the case of the present embodiment, it is easier to set the gap before fixing the magnetic fluid seal 27 and the screw seal 28.

FIG. 10 shows a plan view (a) and a side sectional view (b) of a magnetic disk device to which a spindle unit according to the present invention is applied.

The magnetic disk 20 is mounted inside the cover 32 and fastened to the hub 1 by the clamp 31. The magnetic head 35 is carried by the carriage 33, and the VC
It is driven by M34 to read / write to the magnetic disk 20.

The magnetic disk 20 is mounted on the double-cylindrical hub 1 of the spindle unit in which the bearing 2 and the spindle shaft 5 are fitted and is rotated by the motor 9 including the rotor magnet 7 and the stator coil 8.

The magnetic head 35 is arranged on the magnetic disk 20.
The gap accuracy is set to ± 0.2 micron, but in order to prevent contact or collision between the disk 20 and the head 35, the axial gap accuracy of the bearing 2 is also ±.
0.2 micron is required.

According to this embodiment, since the axial gap of the slide bearing 2 is set by inserting a shim controlled within an error of ± 0.2 micron by machining, the bearing is temporarily formed by molding. Even if the dimensional accuracy of 2 is insufficient,
The gap accuracy of the magnetic head can be reliably ensured.

The magnetic disk device is being miniaturized by standardizing the length, width, and height. However, since the spindle unit, which has the strictest dimensional accuracy control, can be controlled properly, damage to the disk and head is prevented. Not only is it possible to prevent this, but it is also effective in improving the recording density by improving the rotation accuracy.

[0066]

According to the spindle unit of the present invention,
The radial bearing has an arcuate shape, and the thrust bearing has a land taper type dynamic pressure groove.The dynamic pressure effect of the former maintains the axial center, and the dynamic pressure effect of the latter maintains the axial balance to suppress vibration due to rotation. Therefore, there is an effect of improving the safety by improving the rotation accuracy in the compact structure.

According to the spindle unit of the present invention, since the magnetic fluid seal and the screw seal are provided on the outer periphery of the magnetic fluid seal to increase the pressure resistance of the latter, the leakage of the magnetic fluid can be ensured in the miniaturization and high speed operation. There is an effect that can be prevented.

Since the spindle unit according to the present invention is positioned by inserting the shim having a predetermined thickness corresponding to the gap of the thrust bearing during press fitting of the spindle,
Since a gap of less than a micron can be set easily and reliably regardless of the shaft length accuracy of the bearing, the spindle unit can be downsized, and the sliding bearing including the radial and thrust bearings can be integrally molded, enabling mass production. There is an effect that can improve.

According to the magnetic disk device of the present invention, since the magnetic disk is carried on the spindle unit of the present invention, the required miniaturization and rotation accuracy can be ensured, damage to the disk and head can be prevented, and the recording density can be improved. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a spindle unit according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a slide bearing of a spindle unit.

FIG. 3 is a cross-sectional view showing a state transition when setting a clearance in the axial direction of the slide bearing.

FIG. 4 is an explanatory diagram of dynamic pressure distribution due to an arcuate groove of the radial bearing portion of the slide bearing shown in a plan view.

5 is a cross-sectional view taken along the line AA in FIG. 4 and is an explanatory view of dynamic pressure distribution due to the tapered land groove of the thrust bearing portion.

FIG. 6 is an explanatory view showing a state of adjusting the axial position by the dynamic pressure action of the taper land groove.

FIG. 7 is a cross-sectional view showing the axial gap setting state of the slide bearing according to the second embodiment.

FIG. 8 is a vertical sectional view of a spindle unit according to a third embodiment.

FIG. 9 is a cross-sectional view showing a state where an axial gap is set in a slide bearing of a spindle unit according to a third embodiment.

FIG. 10 is a plan view and a side view of a magnetic disk device to which the spindle unit of the present invention is applied.

[Explanation of symbols]

1 ... Hub, 2 ... Slide bearing, 2a ... Radial bearing, 2b
... Thrust bearing, 3 ... Base plate, 4 ... Boss, 5 ...
Spindle shaft, 6 ... Housing, 9 ... Motor, 11, 1
1 '... Thrust receiving plate, 12 ... Shim, 13 ... Magnetic fluid, 1
6, 27 ... Magnetic fluid seal, 17, 28 ... Screw seal,
20 ... Magnetic disk, 23 ... Arc groove, 24 ... Tapered groove,
25 ... Land groove, 26 ... Thrust collar.

Front Page Continuation (72) Inventor Takashi Kono 502 Jinritsucho, Tsuchiura-shi, Ibaraki Machinery Research Institute, Hiritsu Manufacturing Co., Ltd. (72) Inventor Hideaki Amano 2880, Kozu, Odawara-shi, Kanagawa Hitachi Storage Systems Division, (72) Inventor Kenji Tomita, 502, Jinmachi, Tsuchiura-shi, Ibaraki, Institute of Mechanical Research, Hitachi, Ltd.

Claims (14)

[Claims] 1. A spindle unit in which a sliding bearing is fixed to a rotating hub on which an object to be carried is mounted, and a spindle shaft fixed to a base plate is inserted into a radial bearing portion of the bearing. Thrust bearing portions are integrally formed on both end surfaces in the axial direction, and are arranged to face a boss end surface formed on the base plate and a thrust receiving plate fixed to an end portion of the spindle shaft, and the radial bearing portion is disposed. And / or a spindle unit in which a dynamic pressure groove in which a lubricating fluid is sealed is provided in the thrust bearing portion. 2. The spindle unit according to claim 1, wherein the dynamic pressure groove of the radial bearing portion has three grooves of a predetermined arc shape arranged on the inner peripheral surface thereof at equal intervals in the circumferential direction. . 3. The dynamic pressure groove of the thrust bearing portion according to claim 1, wherein grooves having a predetermined taper land shape that is tapered in a rotational direction are symmetrically arranged on the both end surfaces. Characteristic spindle unit. 4. A spindle unit in which a sliding bearing is fixed to a hub on which a supported object is mounted and which is rotated, and a spindle shaft fixed to a base plate is inserted into a radial bearing portion of the bearing. Thrust bearing portions are formed at both ends in the axial direction, and one end portion faces a boss end surface formed on the base plate and the other end faces a thrust receiving plate fixed to an end portion of the spindle shaft. The spindle unit is arranged such that the one end portion is in contact with the boss end surface and a predetermined gap is provided between the other end portion and the thrust receiving plate regardless of the axial length of the slide bearing. . 5. The spindle unit according to claim 4, wherein the predetermined gap is an amount of axial movement of the slide bearing during rotation. 6. The predetermined gap according to claim 4, wherein a shim having a thickness equivalent to the predetermined gap is inserted between the thrust receiving plate and the other end of the slide bearing, and these three members come into contact with each other. A spindle unit, wherein the shim is removed and set after press-fitting the spindle shaft to a position. 7. The press assembly according to claim 4, wherein the spindle shaft is press-fitted so that the end portion of the spindle shaft and the other end portion of the slide bearing are flush with each other,
A spindle unit, comprising: a thrust receiving plate having a stepped portion having a height corresponding to the predetermined gap at a position in contact with the end of the spindle shaft, and fixed to the end of the spindle shaft. 8. The slide bearing according to any one of claims 1 to 7, wherein the radial bearing portion and the thrust bearing portion are integrally formed of a sintered powder alloy or a plastic material. A spindle unit characterized by that. 9. A hub for mounting and carrying an object to be carried, and a hub.
A fixed base plate, a bearing in which the hub is formed into a double cylinder shape and a magnetic fluid is used for lubrication on the innermost side thereof, a rotor magnet inside, and a stator provided at a position facing the rotor magnet of the base plate. In the unit, a magnetic fluid seal formed by arranging a pole piece and a magnet at one end of the inner cylinder of the hub and a predetermined portion of the base plate facing the inner cylinder and a screw seal provided on the outer peripheral portion of the inner cylinder of the hub are provided. A spindle unit characterized by that. 10. The thrust collar according to claim 9, wherein a thrust collar is fitted to an end of the spindle shaft passing through the hub on the side opposite to the magnetic fluid seal, and the end of the thrust collar is opposed to the bearing. And a second magnetic fluid seal and a second screw seal are axially arranged on the outer diameter portion of the thrust collar to be fixed to the hub, and each magnetic fluid seal is double configured at both end portions of the hub. And a spindle unit characterized in that each screw seal is configured to have a uniform pressure resistance. 11. The spindle unit according to claim 9, wherein the pressure resistance of the screw seal is higher than the pressure resistance of the magnetic fluid seal. 12. A method of manufacturing a spindle unit, comprising: mounting a bearing object, fixing a sliding bearing to a rotating hub, and inserting a spindle shaft fixed to a base plate into the bearing. A radial bearing part and thrust bearing parts are integrally formed on the inner peripheral surface of the boss end face formed on the base plate and the other end part of the spindle shaft. A thrust receiving plate fixed to the end of the bearing, a shim having a predetermined thickness is inserted between the thrust receiving plate and the other end of the slide bearing, and the receiving plate, the shim and the other end are inserted. The spindle shaft is press-fitted into the base plate boss hole to a position where the parts come into contact with each other, and then the shim is removed. A method of manufacturing a spindle unit, characterized in that a gap corresponding to a gap is set. 13. A hub on which a magnetic disk is mounted, a fixed base plate, a double cylindrical cylindrical hub, a slide bearing on the innermost side, a rotor magnet inside, and a position facing the rotor magnet on the base plate. In the magnetic disk device driven by providing stators, the slide bearing includes a radial bearing portion on its inner peripheral surface and thrust bearing portions on both ends thereof, and one end portion of the slide bearing portion is a boss formed on the base plate. The other end portion is disposed on the end surface and faces the thrust receiving plate fixed to the end portion of the spindle shaft, and the other end portion and the thrust receiving plate are placed between the thrust receiving plate and the one end portion in contact with the boss end surface. A magnetic disk device characterized in that it has a predetermined gap regardless of the axial length of the slide bearing. 14. The dynamic pressure groove according to claim 13, wherein the radial bearing portion and / or the thrust bearing portion is provided with a dynamic pressure groove in which a magnetic fluid is sealed, and the dynamic fluid flow in the dynamic pressure groove is caused by rotation of the slide bearing. A magnetic disk device, wherein the radial bearing portion balances the axial center position and the thrust bearing portion balances the axial position by a pressure action.