JPH11315827A - Plain bearing - Google Patents

Abstract

(57) [Problem] To provide a sliding bearing which does not leak lubricating fluid even under a reduced pressure environment. A magnetic fluid is used as a lubricating fluid, and a space for holding the expanded lubricating fluid is provided inside the bearing, and a magnetic material is arranged at a portion far from a passage leading from the space to the outside of the bearing, thereby leaking the magnetic fluid. prevent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bearing for supporting a shaft, a spindle motor for rotating an object, and an information recording / reproducing apparatus for recording / reproducing information on / from a disc-shaped information recording medium.

[0002]

2. Description of the Related Art Generally, in a device for recording information on a rotating disk-shaped information recording medium such as an optical disk device or a magnetic disk device, concentric or spiral tracks are provided on the information recording medium, Information is recorded along. In an actual device, there are track swings and bearing vibrations caused by a deviation between the center of rotation and the center of rotation of a concentric circle or a spiral.In order to record or reproduce information along a track, information recording is performed. It is necessary to make the reproducing head follow these swings and vibrations, and to precisely position the head and the track. In order to increase the recording density on the information recording medium, it is necessary to narrow the interval between tracks, and accordingly, the positioning accuracy between the head and the track needs to be stricter.

In order to position the head and the track more precisely, it is effective to reduce the swing and vibration of the track. In particular, in order to reduce the vibration of the bearing, a conventional rolling bearing is used. It is effective to make it an axis. For this reason, it is effective to use a sliding bearing as a bearing for supporting a disc-shaped information recording medium in order to increase the density of an optical disk or a magnetic disk device. When the rolling bearing is changed to a plain bearing, leakage of the lubricating fluid becomes a problem. To solve this problem, a method using a magnetic fluid as the lubricating fluid and using a magnetic seal has been proposed.

[0004] With regard to a sliding bearing using a magnetic fluid as a lubricating fluid, see Journal of Tribologist, Vol.
No., page 464.

As for the magnetic seal, patents such as JP-A-3-51514 and JP-A-5-280545 have been filed.

[0006]

At the time of assembling a slide bearing, fine bubbles may be mixed in the lubricating fluid. This incorporation of air bubbles may not be a problem when used under atmospheric pressure. However, if a sliding bearing with air bubbles mixed in a lubricating fluid is placed in a decompressed environment, the mixed air bubbles expand and leak the lubricating fluid to the outside of the bearing, polluting the environment around the bearing, Insufficient lubrication fluid degrades bearing performance. In order to prevent the leakage of the lubricating fluid from the bearing, a method using a magnetic fluid as the lubricating fluid and using a magnetic seal has been conventionally proposed. The degree is the limit. Therefore, even in the case of a sliding bearing having a magnetic seal, when the environment is lower than the atmospheric pressure by 10 kPa or more, leakage of the lubricating fluid still occurs.

[0007] Even if the operating environment is normally atmospheric pressure, when air cargo is used during transportation, the cargo compartment is in a reduced pressure environment. For example, an aircraft loaded with bearings is 10,000 m high
Atmospheric pressure at that location is about 26.5k
Pa. The pressure difference from the ground is about 74.8 kPa, the lubricating fluid cannot be held by the magnetic seal, and the surroundings may be contaminated during transportation and the performance may be degraded.

As described above, in order to increase the density of an optical disk device or a magnetic disk device, it is effective to use a sliding bearing. However, an optical disk device or a magnetic disk device using a sliding bearing is placed under a reduced pressure environment. In such a case, the above problem occurs.

An object of the present invention is to provide a sliding bearing, a spindle motor, and an information recording / reproducing apparatus which are free from deterioration in performance and contamination of the surroundings even under reduced pressure environment or when transported by air.

[0010]

A sliding bearing having a housing, a bearing metal and a lubricating fluid inside the housing, wherein the lubricating fluid is a magnetic fluid, comprises a space inside the housing, and a space inside the housing and the outside of the housing. And a passage through which air can enter and exit, and further have a magnet inside the housing, and the magnetic fluid created by the magnet draws the magnetic fluid away from the passage. Sliding bearings.

A housing, a bearing having a bearing metal and a lubricating fluid inside the housing, wherein the lubricating fluid is a magnetic fluid; Has a passage through which air can enter and exit, the passage is a gap between the housing and the side surface of the shaft, and further has a magnet inside the housing, and generates a magnetic flux generated by the magnet. A sliding bearing characterized by having a magnetic material that guides to the outer peripheral portion of the space.

A housing, a bearing having a bearing metal and a lubricating fluid inside the housing, wherein the lubricating fluid is a magnetic fluid; a space inside the housing having a shape surrounding a shaft in an annular shape; Has a passage through which air can enter and exit, the passage is a gap between the housing and a side surface of the shaft, and further has a magnet for attracting the magnetic fluid to an outer peripheral portion of the space. A sliding bearing characterized by the following facts.

A rotating shaft, a bearing supporting the rotating shaft, a rotor fixed to the rotating shaft, and a stator fixed to the bearing; a predetermined current is supplied to the rotor or the stator to provide a rotation between the two; A spindle motor in which the rotating shaft rotates around the bearing by the applied torque is a spindle motor wherein the bearing corresponds to claim 1.

A disk-shaped recording medium for recording information magnetically on its surface, a magnetic head for recording and reproducing information on the recording medium by a magnetic method, and rotating the recording medium A spindle motor, an actuator for moving the magnetic head in a radial direction of the recording medium,
The spindle motor according to a command from outside the device;
The actuator; and a system controller for operating a magnetic head to record and reproduce information at a predetermined position on the medium, wherein the magnetic head performs the recording by a fluid force generated by rotation of the recording medium. A magnetic disk device mounted on a slider that moves relative to the medium while floating from the medium, the recording medium, the magnetic head, the spindle motor, and the actuator are provided with an external device and a filter. It is installed in a space where air can enter and exit through
In addition, the magnetic disk drive is characterized by being the spindle motor.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1 is a cross-sectional view of a spindle motor according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram of a state of an oil reservoir, FIG. 3 is an explanatory diagram of an oil reservoir without a yoke of FIG. 1, 4 and 5 are explanatory views of the structure near the bearing metal, and FIG. 6 is a sectional view of the magnetic disk drive.

As shown in FIG. 1, a spindle motor according to a first embodiment of the present invention comprises a shaft 1, a bearing unit 2 for supporting the shaft, a hub 3 fixed to the shaft 1, and a bearing unit 2. It comprises a fixed base 4, a driving magnet 5 fixed to the hub 3, a coil 6, and an iron core 7. Axis 1 is
The bearing unit 2 is fixed in both the thrust direction and the radial direction by a method described later, and is rotatable around its central axis. When a predetermined current flows through the coil 6, magnetization occurs in the iron core 7, and an electromagnetic force acts between the core 6 and the driving magnet 5.

With this force, the shaft 1, the hub 3, the driving magnet 5
Rotates about its central axis. On the hub 3, two magnetic disks 8, 9 with a spacer 10 interposed are mounted.
1 and screws 12, which are also attached to the hub 3.
Rotate with. When rust is generated on the hub 3, oxide fine particles are generated. If this adheres to the magnetic disks 8 and 9, it causes a head crash. Therefore, it is desirable that the hub 3 is made of a material that does not rust.
If the magnetic flux generated by the drive magnet 5 leaks to the magnetic disks 8 and 9, the recorded information may be destroyed. Therefore, the hub 3 is made of a magnetic material to form a magnetic circuit. It is desirable to prevent the magnetic flux generated by the magnet 5 from leaking to the portions of the magnetic disks 8 and 9.

From these facts, the hub 3 is made of SUS420J2, SUS4
It is desirable to use a stainless steel having a magnetic property such as 40C. As described above, the magnetic disk can be rotated by applying the spindle motor according to the first embodiment of the present invention to a magnetic disk device.

As shown in FIG. 1, the bearing unit 2 comprises a metal housing 13, a thrust receiver 14, a lid 15, bearing metals 16, 19, yokes 17, 20, and a magnet 18. Metal housing 13, Thrust receiver 1
The lid 4 and the housing 15 constitute a housing for holding the magnetic fluid 21. In FIG. 1, the magnetic fluid 21 is shown in black. Air bubbles 22 are mixed in the magnetic fluid 21. The bearing metals 16 and 19 have a structure described below, and support the shaft 1 in the radial direction. The drive magnet 5 and the iron core 7 are installed so that their center positions are shifted with respect to the vertical direction in FIG. 1, and the drive magnet 5 receives an attractive force from the iron core 7 in the downward direction in FIG. 1. This force acts on the hub 3 and the shaft 1, and serves as a force for pressing the shaft 1 against the thrust receiver 14. With this force, the shaft 1 is pressed against the thrust receiver 14. As shown in FIG. 1, the end surface of the shaft 1 is processed into a spherical shape, and the thrust receiver 14 is a pivot bearing. The shaft 1 is positioned in the thrust direction by the pivot bearing.

Metal housing 13, Thrust receiver 1
In order to hold the magnetic fluid 21 in the space formed by the four and the lid 15, the magnet 18 is installed in the same space.
The magnet 18 can be made of a normal permanent magnet material, and is magnetized in the direction of the arrow shown in FIG. Since the magnetic fluid 21 is a lubricating fluid for lubricating between the bearing metals 16 and 19 and the shaft 1, it is desirable that the magnetic fluid 21 be supplied as much as possible between the bearing metals 16 and 19 and the shaft 1. for that purpose,
It is effective that the shaft 1 is made of a magnetic material and partially magnetized by the magnet 5 to adsorb the magnetic fluid 21 to the shaft 1. Also,
If rust is generated on the shaft 1, oxide fine particles are mixed into the magnetic fluid 21, which deteriorates bearing performance.

From these facts, the material of the shaft 1 is also SUS420J2,
It is desirable to use magnetic stainless steel such as SUS440C. If the material of the shaft 1 is stainless steel having magnetism such as SUS420J2 or SUS440C, bearing metals 16 and 18, which slide with this, considering problems such as seizure and wear.
The material of the thrust receiver 14 is different from stainless steel,
For example, it is desirable to use a copper-based alloy such as brass.

Air bubbles 22 are mixed in the magnetic fluid 21, and the air bubbles 22 expand under a reduced pressure environment. An oil reservoir 23 is provided between the bearing metal 16 and the lid 15, and the magnetic fluid 21 extruded by the bubbles 22 is held here. A yoke 17 is provided outside the bearing metal 16 so that the magnetic fluid 21 extruded by the bubbles 22 under a reduced pressure environment does not leak from a gap 24 which is a gap between the lid 15 and the side surface of the shaft 1. In general, it is desirable that bubbles such as the bubbles 22 are not mixed into the lubricating fluid, but it is difficult to eliminate the mixing in the actual assembly process.
A structure that does not cause performance degradation and surrounding contamination even when air bubbles are mixed in is required.

The function of the yoke 17 will be described with reference to FIGS. FIG. 2 is an enlarged view of the vicinity of the oil sump 23 in FIG. The upper part of FIG. 2 is at normal atmospheric pressure, and the lower part is at reduced pressure.
The yoke 17 is made of a magnetic material. If the yoke 17 also rusts, the performance of the bearing deteriorates.
It is desirable to use magnetic stainless steel such as SUS440C. As shown in FIG. 1, the yoke 17 is in contact with a magnet 18, and magnetization is generated by a magnetic field generated by the magnet 18. Since the bearing metal 16 is made of a copper-based alloy, it has no magnetism. Therefore, even at normal atmospheric pressure, the magnetic fluid 21 in the oil reservoir 23 is drawn to the yoke 17 as shown in FIG.

When placed in a reduced pressure environment, the air bubbles 22 shown in FIG.
Expands, and the magnetic fluid 21 of that volume flows into the oil reservoir 23. Since the magnetic fluid 21 is attracted to the yoke 17, the magnetic fluid 21 is filled from the larger radius of the oil reservoir 23 as shown in the lower part of FIG. Therefore, lid 15
Only air exists in the gap 24 between the shaft 1 and the side surface of the shaft 1. Even if the bubble 22 in FIG.
No leakage from 4. In this case, the volume of the oil reservoir 23 is required in accordance with the expansion of the mixed air bubbles.

Next, the case where the yoke 17 is not provided will be described, and the necessity of the yoke 17 will be described. FIG. 3 is an enlarged view of the vicinity of the oil sump 23 of FIG. As described above, it is desirable that the shaft 1 is made of a magnetic material. In this case, since the shaft 1 is magnetized by the magnetic field generated by the magnet 18, the magnetic fluid 21 is attracted to the shaft 1 in the oil reservoir 23, as shown in FIG. Under a reduced pressure environment, the bubbles 22 also expand, and the volume of the magnetic fluid 21 enters the oil reservoir 23. When the yoke 17 is not provided, the magnetic fluid 21 is sucked to the shaft 1, and therefore, as shown in the lower part of FIG.
To be satisfied. As shown in the lower part of FIG. 3, when the pressure further decreases from the state where the gap 24 is closed by the magnetic fluid 21,
Since the air confined in the bubbles 22 and the oil reservoir 23 expands, the magnetic fluid 21 leaks from the gap 24 to the outside of the bearing.

Even when the yoke 17 is not provided, the oil reservoir 23 performs its function until the state shown in the lower part of FIG. 3, but since the air is trapped therein, only a part of the volume acts effectively. . If there is a yoke 17 in comparison,
Since the oil reservoir 23 is filled with the magnetic fluid 21 from a location far from the gap 24, the entire volume of the oil reservoir 23 can be effectively used. The same effect can be obtained by using the yoke 17 as a magnet magnetized in the vertical direction in FIG. Even when the yoke 17 is provided, since the shaft 1 is magnetized by the magnet 18, the magnetic fluid 21 in the oil reservoir 23 is also attracted to the shaft 1. However, while the yoke 17 is in close contact with the magnet 18, the axis 1 is separated from the magnet 18, so that the magnetization of the yoke 17 is larger than the magnetization of the oil reservoir 23 of the axis 1, Is larger than the suction force of the shaft 1. Therefore, when the yoke 17 is provided, the magnetic fluid 21 in the oil reservoir 23 is sucked into the yoke 17.

FIGS. 4A and 4B show the structures of the bearing metal 16 and the yoke 17 in more detail. The upper part is a plan view, and the lower part is a sectional view. The bearing metal 16 has four bearing surfaces 31, 32, 33, 34 and four oil grooves 35, 36, 3.
7,38. The shaft 1 rotates counterclockwise when viewed from the direction shown in FIG.
The shaft 1 is radially supported by the fluid forces acting on the side surfaces of the shaft 1, 32, 33, and 34. The yoke 17 is located on the outer periphery of the bearing metal 16. The bearing metal 19 has the same structure as the bearing metal 16, and the yoke 20 has the same structure as the yoke 17. The yoke 20 may be omitted, but it is desirable to use the same components for cost reduction, so that the yoke 20 has the same structure.

FIGS. 4A and 4B illustrate the case of a so-called four-arc bearing, but it is also possible to use a three-arc bearing as shown in FIGS. 5A and 5B.

FIG. 6 is a sectional view of a magnetic disk drive on which the spindle motor described with reference to FIGS. 1 to 5 is mounted. The bearing unit 2 is mounted on the base 4, and the hub 3 rotates around a rotation axis defined by the bearing unit 2. Magnetic disks 8, 9, and a spacer 10 are fixed to the hub 3 by a clamper 11 and screws 12. Is as described above. The magnetic disk device is connected to the outside of the device by a connector 52, and receives instructions for power supply and information recording / reproduction, receives information to be recorded, and outputs the reproduced information. An electric circuit for operating the magnetic disk device is formed on the substrate 51.

When power is supplied from the connector 52,
The substrate 51 supplies a predetermined current to the coil 6 of FIG. 1 provided in the hub 3 of FIG. 6, and the hub 3 and the magnetic disks 8, 9 fixed to the hub 3 rotate. A plurality of tracks are provided concentrically on the magnetic disks 8 and 9, and information is recorded by magnetic marks formed along the tracks. As shown in FIG.
Head 63 for the track provided on the upper surface of
A head 64 is provided for a track provided on the lower surface of the magnetic disk 9, a head 65 is provided for a track provided on the upper surface of the magnetic disk 8, and a head 65 is provided for a track provided on the lower surface of the magnetic disk 8. The head 66 records and reproduces information.

To record and reproduce information, the head 6
3, 64, 65, 66 must be moved in the radial direction of the magnetic disks 8, 9 and positioned at predetermined track positions. This function is performed by the shaft 55, the actuator bearing 56, the arms 59, 60, 61, 62, the coil 5
7. The magnetic circuit 58. The shaft 55 is fixed to the base 4, and the actuator bearing 56 rotates around the central axis of the shaft 55. The arm 5 is provided on the actuator bearing 56.
9, 60, 61, 62 are fixed, and the arms 59,
Heads 63, 64, 65, 6 are provided at the tips of 60, 61, 62.
6 is fixed. Actuator bearing 56 is shaft 55
By rotating around the central axis of the heads 63, 6
4, 65, 66 move in the radial direction of the magnetic disks 8, 9.

A coil 57 is fixed to the actuator bearing 56. A magnetic field is applied to the coil 57 by a magnetic circuit 58. When a current flows, a Lorentz force acts on the coil 57, and the coil 57 becomes a torque for rotating the actuator bearing 56. In a track provided on the upper surface of the magnetic disk 9, there is provided a mark for generating a signal indicating a positional deviation between the track and the head 63. When the head 63 passes over this mark, the head 63 The signal generated from 63 is input to the board 51 and is converted into a signal indicating a positional shift by an electric circuit in the board 51. By feeding back this signal to the coil 57, the head 63 is positioned on a predetermined track provided on the upper surface of the magnetic disk 9. The same applies to the method of positioning the heads 64, 65, 66 on predetermined tracks.

When a signal recording command is input from the connector 52, the board 51 determines which track to record on based on the command. Hereinafter, description will be made assuming that this track is provided on the upper surface of the magnetic disk 9. The same applies to the case where it is provided on another surface. After making the determination, the substrate 51 supplies a current to the coil 57 to position the head 63 on the track on which recording is to be performed. A mark for identifying each track is provided on the track, and it is possible to confirm whether or not the head 63 is positioned on a predetermined track by a signal obtained from the mark. If the substrate 51 is not positioned on a predetermined track, the substrate 51 supplies a current to the substrate 57 again and performs positioning again. After the positioning on the predetermined track is confirmed, the substrate 51 supplies a current corresponding to the information to be recorded to the head 63, and forms a magnetic mark on the track to record the information.

When a command to reproduce a signal is input from the connector 52, the board 51 determines from which track to start reproduction based on the command. Hereinafter, description will be made assuming that this track is provided on the upper surface of the magnetic disk 9.
The same applies to the case where it is provided on another surface. The positioning method for a predetermined track is the same as that for recording. After the positioning on the predetermined track is confirmed, the substrate 51 performs predetermined processing on the signal obtained from the head 63 and outputs the signal from the connector 52.

A lid 67 is attached to the base 4 and the space between the two is sealed so that air cannot enter or exit from a gap between the two. Also, base 4
The bearing unit 2 is also hermetically sealed, so that air cannot enter or exit from the gap between the two. The space between the base 4 and the shaft 55 is similarly sealed. The coil 6 existing in the hub 3 and the heads 63, 64, 65, 6
6, a connector 54 is provided on the base 4 and a connector 53 is provided on the substrate 51 for exchanging electric signals and electromagnetic energy between the coil 57 and the substrate 51.

The connectors 53 and 54 are connected, and the board 51 and the coil 6 existing in the hub 3 and the head 6
Signals and energy can be exchanged with the 3, 64, 65, 66 and the coil 57. The space between the connector 54 and the base 4 is also hermetically sealed, and the connector 54 itself has a structure in which air cannot enter or exit. A filter 68 is provided on the base 4, and air can enter and exit the space between the base 4 and the lid 67 and the outside of the apparatus only through the filter 68. In a normal environment, the base 4 and the lid 67
The space between is usually filled with air at atmospheric pressure.

The head 63 comprises a slider 71 and a magnetic head 72, as shown in FIG. Head 6
The disk peripheral speed due to the rotation of the magnetic disk 9 at the position 3 is V, which rotates in the direction of the arrow drawn near V in FIG. As described above, the base 4 and the lid 67
The space between is usually filled with air at atmospheric pressure,
As the magnetic disk 9 rotates, an airflow is generated near the magnetic disk 9. The slider 71 moves the slider 71 from the magnetic disk 9 at a predetermined distance h
It keeps floating. Recording and reproduction of information is performed by the slider 7
The recording and reproduction of information is difficult if the distance h between the slider 71 and the magnetic disk 9 is too large.
The risk of collision between the disk and the magnetic disk 9 for some reason increases. Therefore, the distance h between the slider 71 and the magnetic disk 9 needs to be within a certain range.

As a parameter affecting the distance h between the slider 71 and the magnetic disk 9, there is a pressure in the space between the base 4 and the lid 67. If the space between the base 4 and the lid 67 is sealed, the pressure in the space between the base 4 and the lid 67 changes due to, for example, a rise in temperature due to the operation of the apparatus or a change in the temperature of the surrounding environment. I will. As a result, the distance h between the slider 71 and the magnetic disk 9 changes. Usually, the magnetic disk drive is used under normal atmospheric pressure. Therefore, if air can enter and exit between the space between the base 4 and the lid 67 and the outside of the apparatus, the pressure in the space between the base 4 and the lid 67 can be kept substantially constant.

As shown in FIG. 7, the magnetic disk 9 has a structure in which a magnetic recording film 74 is formed on a substrate 75 and a protective film 73 is formed thereon. The arrow drawn on the magnetic recording film 74 indicates the direction of magnetization in the magnetic recording film 74.
A mark is formed by a pattern of magnetization, and information is recorded. If dust is mixed in the air filling the space between the base 4 and the lid 67, the dust is
When the magnetic recording medium 74 is caught between the magnetic disk 1 and the magnetic disk 9, the magnetic recording film 74 is destroyed, and the recorded information is destroyed.

In order to prevent this, the protective film 73 is formed. Depending on the hardness, size, and number of dust, the protective film 73 may be broken through and the magnetic recording film 74 may be broken. Therefore, it is desirable that the air filling the space between the base 4 and the lid 67 contains almost no dust. If this magnetic disk drive is assembled in a clean environment such as a clean room, immediately after assembling,
Dust can hardly be contained in the air filling the space between the base 4 and the lid 67.

As described above, it is desirable that air can enter and exit from the space between the base 4 and the lid 67 and the outside of the apparatus.
Since the outside of the apparatus is usually in a normal environment, dust is generally mixed with air. Therefore, a place where air can enter and exit is limited, and a filter 68 is provided there to remove dust when air enters the space between the base 4 and the lid 67 from outside the apparatus. This keeps the air filling the space between the base 4 and the lid 67 clean,
The pressure can be kept almost constant.

When this magnetic disk device is placed in a decompressed environment, the bubbles 22 in the bearing unit 2 expand. However, the bearing unit 2 has the above-described structure, so that the magnetic fluid 21 does not leak, and The pollution and the performance of the bearing will not deteriorate.

In a normal magnetic disk drive, concentric tracks are provided on an information recording medium, and information is recorded along the concentric tracks. In an actual device, there is a track swing or a bearing vibration caused by a deviation between the center of the concentric circle and the center of rotation.In order to record or reproduce information along the track, information recording and reproduction must be performed. It is necessary that the magnetic head to be performed follow these swings and vibrations to precisely position the head and the track. In order to increase the recording density on the information recording medium, it is necessary to narrow the interval between the tracks, and accordingly, the positioning accuracy between the head and the track needs to be stricter.

In order to position the head and the track more precisely, it is effective to reduce the swing and vibration of the track. In particular, in order to reduce the vibration of the bearing, a conventional rolling bearing is used. It is effective to make it an axis. For this reason, it is effective to slide the bearing that supports the disc-shaped information recording medium to increase the density of the magnetic disk drive. When the rolling bearing is changed to a plain bearing, leakage of the lubricating fluid becomes a problem. To solve this problem, a method using a magnetic fluid as the lubricating fluid and using a magnetic seal has been proposed.

As described above, when assembling the slide bearing,
Fine bubbles may be mixed in the lubricating fluid. This incorporation of air bubbles may not be a problem when used under atmospheric pressure. However, if a sliding bearing with air bubbles mixed in a lubricating fluid is placed in a decompressed environment, the mixed air bubbles expand and leak the lubricating fluid to the outside of the bearing, polluting the environment around the bearing, Insufficient lubrication fluid degrades bearing performance. In order to prevent the leakage of the lubricating fluid from the bearing, a method using a magnetic fluid as the lubricating fluid and using a magnetic seal has been conventionally proposed. The degree is the limit. Therefore, even if a sliding bearing having a magnetic seal is placed in an environment lower than atmospheric pressure by 10 kPa or more,
Again, leakage of the lubricating fluid occurs.

Even if the operating environment is normal atmospheric pressure, when air cargo is used during transportation, the cargo compartment is in a reduced pressure environment. For example, an aircraft loaded with bearings is 10,000 m high
Atmospheric pressure at that location is about 26.5k
Pa. The pressure difference from the ground is about 74.8 kPa, the lubricating fluid cannot be held by the magnetic seal, and the surroundings may be contaminated during transportation and the performance may be degraded.

As described above, in order to increase the density of the magnetic disk device, it is effective to use a sliding bearing. However, when the magnetic disk device using the sliding bearing is placed in a reduced pressure environment, the above-described method is used. Problems arise. According to the present invention, it is possible to configure a sliding bearing, a spindle motor, and a high-density magnetic disk device using the same without deteriorating the performance or contaminating the surroundings even when transported under reduced pressure environment or by air mail.

A second example of the embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a sectional view of a spindle motor according to a second embodiment of the present invention.
Is an explanatory view of the state of the oil reservoir, and FIG. 10 is a structural view of the bearing metal.

In a second example of the embodiment of the present invention, an example applied to an optical disk device will be described.

FIG. 8 shows a spindle motor shaft 1, bearing unit 2, hub 3, base 4, drive magnet 5, coil 6, iron core 7, and metal housing 13 as a second embodiment of the present invention shown in FIG. The structure and function of the thrust receiver 14, lid 15, magnet 18, and magnetic fluid 21 are the same as those in the first embodiment of the present invention. As in the case of the first example, air bubbles 22 are mixed in the magnetic fluid 21. Unlike the first example, in the second example, the yokes 17, 2
0 is not provided, and a magnet 41 is provided in the oil reservoir 23. Further, a chucking mechanism 43 is fixed to the shaft 1, and by rotating the shaft 1, the optical disk 42 attached to the chucking mechanism 43 can be rotated. The structure of the bearing metals 45 and 46 will be described later. Thus, the optical disk can be rotated by applying the spindle motor according to the second embodiment of the present invention to the optical disk device.

The function of the magnet 41 will be described with reference to FIG. The magnet 41 can use a normal magnet material,
It is magnetized as shown in the upper part of FIG. For this reason,
The magnetic fluid 21 in the oil reservoir 23 is attracted by the magnet 41.
When this spindle motor is placed in a reduced pressure environment, the bubbles 22 shown in FIG. 8 expand. Expanded volume of magnetic fluid 21
Flows into the oil sump 23. The inflowing magnetic fluid 21 is attracted to the magnet 41 as shown in the lower part of FIG.
4, only air leaks, and the magnetic fluid 21 does not leak. In an ordinary optical disk device, a spindle motor is installed in a space where air can enter and exit from the outside of the device.
Therefore, when the optical disk device is placed in a reduced pressure environment, the spindle motor is necessarily placed in a reduced pressure environment. When the spindle motor according to the second embodiment of the present invention is applied to an optical disk, it is possible to configure an optical disk device free from surrounding contamination and performance degradation even in a reduced pressure environment.

FIGS. 10A and 10B show the structure of the bearing metals 45 and 46 of FIG. The shape of the bearing surface is a perfect circle. As shown in FIG. 8, a groove 44 is provided on the shaft 1, and the shaft 1 is supported in the radial direction by the fluid force generated at this portion.

[0053]

According to the present invention, it is possible to construct a sliding bearing, a spindle motor, a magnetic disk device, and an optical disk device that are free from performance degradation and surrounding contamination even in a reduced pressure environment or when transported by air. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor according to an embodiment of the present invention.

FIG. 2 is an enlarged view of an oil sump.

FIG. 3 is an enlarged view of an oil sump.

4A and 4B are a plan view showing a structure of a bearing metal and a yoke, and a cross-sectional view of FIG. 4A.

FIGS. 5A and 5B are a plan view showing a structure of a bearing metal and a yoke, and a cross-sectional view of FIG. 5A.

FIG. 6 is a structural view of a magnetic disk drive.

FIG. 7 is a structural diagram of a head.

FIG. 8 is a sectional view of a spindle motor which is an example of the embodiment of the present invention.

FIG. 9 is an enlarged view of an oil sump.

10A and 10B are a plan view showing a structure of a bearing metal and a cross-sectional view of FIG. 10A.

[Explanation of symbols]

1, 55: shaft, 2: bearing unit, 3: hub, 4: base, 5: drive magnet, 6, 57: coil, 7: iron core, 8,
9 magnetic disk, 10 spacer, 11 clamper,
12 ... screw, 13 ... metal housing, 14 ... thrust receiver, 15, 67 ... lid, 16, 19, 45, 46 ... bearing metal, 17, 20 ... yoke, 18, 41 ... magnet, 2
DESCRIPTION OF SYMBOLS 1 ... Magnetic fluid, 22 ... Bubble, 23 ... Oil reservoir, 24 ... Gap, 31, 32, 33, 34 ... Bearing surface, 32, 36, 3
7, 38 oil groove, 42 optical disk, 43 chucking mechanism, 44 groove, 51, 75 substrate, 52, 5
3, 54 ... connector, 56 ... actuator bearing, 58
... magnetic circuit, 59, 60, 61, 62 ... arm, 63,
64, 65, 66: head, 68: filter, 71: slider, 72: magnetic head, 73: protective film, 74: magnetic recording film.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor, Katsutoshi Arai 502, Kandachicho, Tsuchiura-shi, Ibaraki Pref. Inside the Machine Research Laboratory, Hitachi, Ltd. Within the Machinery Research Laboratory (72) Inventor Yuichi Yanase 502, Kandachi-cho, Tsuchiura-shi, Ibaraki Pref.Mechanical Research Laboratory, Hitachi, Ltd. (72) Inventor Kenji Tomita 2880, Kofu, Odawara-shi, Kanagawa Pref.

Claims (1)

[Claims] 1. A sliding bearing having a housing, a bearing metal and a lubricating fluid inside the housing, wherein the lubricating fluid is a magnetic fluid, wherein a space is formed inside the housing, and between the space and the outside of the housing. A sliding bearing having a passage through which air can enter and exit, and further having a magnet inside the housing, wherein the magnetic fluid is attracted to a position away from the passage by a magnetic field generated by the magnet.