JPH0354782A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent the rotational center of a magnetic disk from being deviated by providing an interval between inner and outer hubs, for which the coefficient of thermal expansion is made almost equal, and lowering the rigidity of the outer hub rather than the rigidity of the magnetic disk and a spacer. CONSTITUTION:An interval G is provided in one spot at least between an inner hub 46, which holds a permanent magnet 47 in an inner peripheral part, and an outer hub 45 holding plural magnetic disks 1 in an outer peripheral part. For the inner and outer hubs 46 and 45, the coefficient of thermal expansion is made almost equal and the rigidity of the outer hub 45 is made lower than the rigidity of the magnetic disk 1, which is held by the outer hub 45, and a spacer 2. Thus, the rotational center of the magnetic disk is prevented from being deviated with the fluctuation of an environmental temperature and the off-track of the magnetic head is prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk device, and particularly to a technique for fixing a magnetic disk, which is a storage medium, to a spindle motor.

[Conventional technology]

For example, in magnetic disk drives installed as external storage devices in office processing equipment such as personal computers and word processors, market demands have led to further miniaturization and an increase in the information storage capacity per unit device. has been done.

In order to increase the storage capacity per unit device, measures such as increasing the number of magnetic disks used as storage media, or increasing the number of tracks by narrowing the spacing between the tracks arranged concentrically on each magnetic disk are taken. is taken.

On the other hand, in the field of relatively small magnetic disk drives, 5.
2. As the names such as 5-inch disks and 3.5-inch disks are commonly used, the external dimensions of magnetic disk drives are precisely defined based on the diameter of the magnetic disk that is the storage medium due to the history of popularization. Therefore, in order to cope with the increase in storage capacity, high-density packaging of magnetic disks is essential.

Furthermore, the operating environment of office processing equipment such as personal computers and word processors, which are the main applications for small magnetic disk drives, is generally harsh and subject to temperature fluctuations.

For this reason, the characteristics required of the spindle motor that holds and rotates the magnetic disk in a magnetic disk device are that it is small, and that the degree of eccentricity of the center of rotation and thermal deformation of the magnetic disk due to environmental temperature fluctuations is small. is required.

In other words, as mentioned above, the track spacing is becoming narrower in response to the demand for increased storage capacity, and even slight eccentricity or deformation of a magnetic disk can affect information recording/reproducing operations on the magnetic disk. This is because it causes what is called off-track, in which the magnetic head deviates from the target track, impairing the reliability of the operation of the magnetic disk device.

For this reason, in the past, the motor structure was coaxially wrapped around a hub, and the magnetic disk was held and rotated by this hub, so-called in-hub technology.
The outer rotor type is the mainstream, and especially regarding the structure of the hub, for example,
Techniques disclosed in Publication No. 2 and the like have been proposed.

That is, the hub that holds the magnetic disk has a double structure in which the inner cylindrical member that holds the permanent magnet is made of iron, and the outer sleeve that holds the magnetic disk is made of the same type of aluminum alloy as the magnetic disk. By joining the hubs at the center by shrink fitting, etc., and leaving gaps at both ends, the heat on the magnetic disk side caused by the fact that the entire hub is made of iron, which has a different coefficient of thermal expansion than the magnetic disk, is reduced. In addition to alleviating deformation, the cylindrical member supported by the steel shaft via the bearing is made of the same material as the steel shaft to prevent pressure fluctuations in the bearing in the axial direction.

[Problem to be solved by the invention]

However, in the case of the above-mentioned conventional technology, if the shrink fitting of two types of members with different coefficients of thermal expansion is not performed correctly, the state of bonding between them changes due to fluctuations in environmental temperature, and the outer aluminum No consideration was given to the fact that the rotation center of the magnetic disk held in the sleeve would shift from its normal position due to torsional deformation of the sleeve made of the same material.

In order to prevent this, it is necessary to control processing and assembly processes more strictly than necessary, but there is a limit to this from the viewpoint of manufacturing costs.

For this reason, in a double-structured hub made of different materials, off-track as described above is likely to occur, resulting in a problem of lowering the reliability of the operation of the magnetic disk device.

In addition, thermal deformation occurs on the hub side due to the difference in thermal expansion coefficient between the permanent magnet installed inside the hub and the hub.
In order to avoid this, if a structure is adopted in which the permanent magnet is divided in the circumferential direction, there is a problem that the assembly work becomes complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic disk device that can prevent the center of rotation of a magnetic disk from shifting due to fluctuations in environmental temperature.

Another object of the present invention is to provide a magnetic disk device with high operational reliability.

Still another object of the present invention is to provide a magnetic disk device that can prevent the negative influence on a magnetic disk caused by a permanent magnet that guards a spindle motor.

Still another object of the present invention is to provide a magnetic disk device that can realize stable operation for a long time.

Still another object of the present invention is to provide a magnetic disk device that is easy to assemble.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the magnetic disk device according to the present invention includes a plurality of magnetic disks that function as storage media, a spindle motor that generates rotational force, and a part of the spindle motor that drives the plurality of magnetic disks at predetermined intervals of M. A hub that rotates while being held substantially coaxially; a spacer that is interposed between adjacent magnetic disks to define the spacing between the magnetic disks; a disk clamp that is fixed to the hub by pressing; a group of magnetic heads that are arranged to face the magnetic disk and perform at least one of recording and reproducing information on the magnetic disk; A magnetic disk device comprising a drive mechanism that performs positioning operation in the radial direction, the hub comprising:
It is composed of an inner hub that holds a permanent magnet on its inner periphery and an outer hub that holds multiple magnetic disks on its outer periphery, and there is at least one gap between the inner hub and the outer hub. The coefficients of thermal expansion of the inner hub and the outer hub are approximately equal, and the rigidity of the outer hub is lower than the rigidity of the magnetic disk and spacer held by the outer hub.

[Effect]

According to the above-described magnetic disk device of the present invention, since the coefficients of thermal expansion of the inner hub and the outer hub that control the hub are almost equal, it is possible to avoid unnecessarily strict machining or assembly even when the environmental temperature fluctuates. No distortion that would change the concentricity occurs at the joint between the two.

In addition, by thinning the wall surface of the outer hub and reducing its rigidity by forming cutouts, the outer hub side deforms by following the thermal deformation of the magnetic disk sandwiched between the outer hub and the disk. Therefore, radial distortion does not occur in the magnetic disk due to restraint of thermal deformation of the magnetic disk.

Furthermore, by constructing the spacer interposed between the plurality of magnetic disks using a material having a coefficient of thermal expansion equivalent to that of the hub, the coefficient of thermal expansion of the aggregate consisting of the spacer and the magnetic disks becomes almost equal to that of the hub side. Thermal stress acting on the magnetic disk is alleviated.

In addition, the contact portions of the outer hub and the disk clamp with respect to the magnetic disk are connected to first and second wires that have approximately the same coefficient of thermal expansion as the magnetic disk, and that are approximately coaxial and have the same diameter in line contact with the magnetic disk. By using the contact pieces, the force that tends to deform the magnetic disk in the radial direction, which is generated by thermal deformation of the outer hub and the disk clamp, uses the contact line of the first and second contact pieces as a fulcrum. Since it is absorbed by the tilting motion, it is not transmitted to the magnetic disk, and deformation of the magnetic disk in the radial direction can be avoided.

This eliminates the deviation of the center of rotation of the magnetic disk due to fluctuations in environmental temperature, prevents off-track of the magnetic head that records/reproduces information on the rotating magnetic disk, and prevents the operation of the magnetic disk drive. reliability is improved.

In addition, by manufacturing the inner hub and outer hub from the same material as the shaft of the spindle motor that supports the inner hub and outer hub through the bearing, pressure fluctuations in the axial direction of the bearing due to temperature changes are eliminated. As a result, the life of the bearing is extended, and stable operation over a long period of time can be achieved.

In addition, the inner hub and the outer hub are made of magnetic material, a gap is provided between the inner hub and the outer hub over the entire circumference, and the structure is such that the inner hub and the outer hub are connected at the large diameter portion of the insertion end of the outer hub. By doing so, the thermal deformation of the permanent magnet placed in the axial center of the inner hub will not be transmitted to the outer hub side, eliminating the need for measures such as dividing the permanent magnet in the circumferential direction, and reducing the number of parts. , the assembly work of the magnetic disk device is simplified.

Further, due to the shielding effect of the inner hub and the outer hub made of magnetic material, the negative magnetic influence of the permanent magnet in the inner hub is prevented from reaching the magnetic disk held by the outer hub.

[Embodiment 1] Hereinafter, a magnetic disk device that is an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of the structure of a main part of a magnetic disk device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing an example of its overall structure, and FIG. FIG. 2 is a diagram illustrating an example of the operation of the magnetic disk device of this embodiment.

First, the overall structure will be explained with reference to Figure 2.

A cover 14, which also has a concave cross section, is tightly attached to the base 11, which has a concave cross section, through a packing 15, and protects a sealed space 8 that is cut off from the outside.

Inside this sealed space A, a spindle motor 4 having a motor shaft 4l is housed. One end of the motor shaft 41 is supported on the base 11 side via a motor base 42 and a screw 18, and the other end is supported on the cover 2 side via screws 19.

A plurality of magnetic disks 1 are arranged at predetermined intervals in the axial direction with a plurality of disk spacers 2 in between, surrounding a cylindrical outer hub 45 (described later) that constitutes a spindle motor 4 and rotates around a motor shaft 41. They are mounted parallel to each other.

These magnetic disks 1 and disk spacers 2 are
The outer hub is compressed in the axial direction between the disk clamp 3 attached to one end of the outer hub 45 via the screw 21 and the flange portion 45a provided at the other end of the outer hub 45. 45 so that it can be stably held and rotated.

Furthermore, one end of the spindle motor 4 is fixed to the base 11 in a position parallel to the motor shaft 4l,
A pivot shaft 12 is provided, the other end of which is supported by a cover 14 via a screw 20.

A cylindrical hub carriage 13 having a flange portion 13a at its lower end is coaxially and rotatably mounted on the pivot shaft l2. The outside of this hub carriage 13 FRII
A plurality of head arms 5a and a coil frame 8a having a voice coil 8 wound around one end thereof are attached to the head arm S at predetermined intervals in the axial direction by interposing a plurality of head spacers 7. The tip of 5a is
It extends to a position to sandwich a plurality of magnetic disk drives fixed at predetermined intervals in the axial direction of the spindle motor 4.

The head arm 5a, head spacer 7, and coil frame 8a mounted on the hub carriage 13 so as to be stacked in the axial direction are attached to the flange portion 1 by a head clamp 10 mounted on the upper end of the hub carriage 13.
3a, it is stably fixed by being compressed in the axial direction, and has a structure in which it rotates as a unit around the pivot axis l2.

Voice coil 8 wound around one end of coil frame 8a
constitutes a voice coil motor VCM together with a fixed magnet 9 fixed to the side of the base 1l so as to intersect the voice coil 8, and the direction and magnitude of the current applied to the voice coil 8 can be adjusted as appropriate. By doing so, the rotation direction, rotation amount, speed, etc. of the hub carriage 13 to which the coil frame 8a is fixed, that is, the head arm 5a, are controlled.

At the tip of each of the plurality of head arms 5a, which are positioned to sandwich the plurality of magnetic disks 1, a plurality of magnetic disks arranged to face each of the recording surfaces of the magnetic disks l are attached via leaf springs 5b. A head 5 is supported, and the rotation of the hub carriage 13 by the voice coil motor VCM allows positioning of the magnetic disk 1 to any position in the radial direction.

Among the plurality of magnetic heads 5, one located at the center in the axial direction of the spindle motor 4 functions as a servo head 6.

That is, on the recording surface of the magnetic disk l that the servo head 6 faces, servo tracks (position information) indicating the position in the radial direction are recorded in advance in a concentric manner.
By feeding back this positional information read by the servo head 6 to the control of the voice coil motor VCM, precise positioning control of another group of magnetic heads 5 fixed to the hub carriage 13 and moving together with the servo head 6 is performed. is to be carried out.

A communication hole 16a that communicates the closed space A with the outside is formed in a part of the base l1, and a high-performance filter 16 for removing fine dust and the like is attached to this communication hole 16a. ing. As a result, the base 11 and cover 14 that constitute the sealed space A are created by the pressure difference between the sealed space 8 and the outside.
This prevents troubles such as deformation and misalignment of the spindle motor 4 and hub carriage l3.

Also, on the bottom surface of the base 11 is a voice coil motor VC.
A control board 17 is mounted on which an electric circuit for controlling the positioning operation by M and the rotational operation of the spindle motor 4 is constructed.

For example, in the case of a 5.25-inch magnetic disk drive, all of the above-mentioned components are 82. 6 m
It is mounted within the external dimensions of (height) x 146mm (width) x 203u (depth).

Here, in the case of this embodiment, the spindle motor 4 holding a plurality of magnetic disks l is inserted into an outer hub 45 and the outer hub 45, as shown in FIG. Part of the outer hub 4 is
The outer hub 45 is rotatably supported by the motor shaft 41 via a bearing 44a, and the inner hub 46 is rotatably supported by the motor shaft 41 via a bearing 44b.
41 so as to be rotatable.

A coil 43 that generates a rotating magnetic field is attached to the outer periphery of the central part of the motor shaft 41 that is stationary supported by the base 11 and the cover 14, and a coil 43 that generates a rotating magnetic field is attached to the inner periphery of the inner hub 46 that surrounds the coil 43. position,
That is, a cylindrical permanent magnet 47 is attached at a position away from the large diameter B46a that connects to the outer hub 45,
The interaction between the coil 43 and the permanent magnet 47 causes the inner hub 46 and the outer hub 45 to rotate.

A well-known magnetic fluid sealing mechanism 48a and a magnetic fluid sealing mechanism 48b are arranged outside the bearing 44a and the bearing 44b that support the outer hub 45 and the inner hub 46, respectively, and the bearing 44a inside the spindle motor 4, Dust generated from the magnetic disk 44b and the like is prevented from flowing into and contaminating the clean closed space 8 where the magnetic disk 1 is located.

In this case, by reducing the thickness of the outer hub 45 that holds the plurality of magnetic disks 1, the rigidity of the outer hub 45 is intentionally made higher than the rigidity in the overlapping direction of the aggregate composed of the magnetic disks 1 and disk spacers 2. I'm trying to keep it low.

Further, the outer hub 45 and the inner hub 46 are made of an iron-based magnetic material similar to the motor shaft 41, and are connected to each other through a large diameter portion 46a partially formed at the inner end of the inner hub 46. coaxially and integrally connected,
The outer hub 4
5 and the outer diameter of the inner hub 46 are set.

The large-diameter portion 46a of the inner hub 46 and the outer hub 45 are coupled to each other by, for example, pressing, adhesion, or shrink fitting. Note that the joint portion by the large diameter portion 46a does not need to be continuous in the circumferential direction;
A structure in which grooves are carved at equal intervals in the circumferential direction may be used.

In that case, by installing a QIJ ring or the like over the entire circumferential direction of the large diameter portion 46a, dust inside the spindle motor 4 can be prevented from flowing out to the side of the closed space 8 where the magnetic disk l is accommodated. To prevent.

Furthermore, the disk clamp 3 that fixes the plurality of magnetic disks 1 and disk spacers 2 to the outer hub 45 is an inner clamp that is in contact with the outer hub 45 and is made of a material having the same coefficient of thermal expansion as the outer hub 45. 3a, and an outer clamp 3b (second contact piece) that is in contact with the magnetic disk 1 and is made of a material having the same coefficient of thermal expansion as the magnetic disk 1, and both are connected to the outer periphery of the inner clamp 3a. They are joined together by methods such as gluing or shrink fitting.

Further, in this case, the outer clamp 3b in contact with the magnetic disk 1 is a ring having a convex cross-sectional shape on the side of the magnetic disk l, and is configured to be in line contact with the magnetic disk 1 over the entire circumference around the outer hub 45. It has become.

Similarly, the flange W=4 of the outer hub 45 that clamps the plurality of magnetic disks 1 with this disk clamp 3
A contact member 49 (l-th contact piece) made of a material having a coefficient of thermal expansion equivalent to that of the magnetic disk l is attached to the contact portion with respect to the disk 1.

The abutting member 49 has a ring shape in cross section that is convex toward the magnetic disk 1 side, and is in line contact with the magnetic disk l over the entire circumference around the outer hub 45.

Further, the diameter of the circular line contact area of this abutting member 49 is coaxial with and has the same diameter as the circular line contact area of the outer clamp 3b of the disk clamp 3 with respect to the magnetic disk 1. When compressing the magnetic disk 1 and the disk spacer 2 in the axial direction, generation of bending stress that would deform the magnetic disk 1 in the radial direction is prevented.

The operation of the magnetic disk device of this embodiment having the above-described structure will be explained below.

For example, when the temperature of each part of the magnetic disk device rises due to fluctuations in the environmental temperature or heat generated from the spindle motor 4 and voice coil motor VCM during operation, the temperature of each part of the magnetic disk drive increases. The spacer 2 thermally expands, and at the same time, the outer hub 45 and inner hub 45 holding them also thermally expand.

At this time, in the case of this embodiment, since the outer hub 45 and the inner hub 46 are made of materials having the same coefficient of thermal expansion, there is no need to process the joint between them more strictly than necessary. Unlike the conventional case in which the two are made of materials with different coefficients of thermal expansion, there is no variation in coaxiality due to temperature changes, that is, thermal eccentricity.

Furthermore, since the rigidity of the outer hub 45 is set lower than that of the aggregate of the magnetic disk l and the disk spacer 2, even if there is a difference in the coefficient of thermal expansion between the two, the outer hub 45
Since the side 5 deforms following the thermal deformation of the magnetic disk 1 and the disk spacer 2, large thermal stress that restrains the assembly consisting of the magnetic disk 1 and the disk spacer 2 is not generated. Therefore, distortion and deformation in the radial direction of the magnetic disk l is prevented.

For example, the magnetic disk l and the disk spacer 2 are made of aluminum (coefficient of thermal expansion: 24X10-''/℃>, and the outer hub 45 is made of iron (coefficient of thermal expansion: 24X I O-'/t).
), and if the thickness of the thin portion of the outer hub 45 is 1/4 of the radial thickness of the disk spacer 2, then the amount of deformation of the magnetic disk l in the radial direction is as shown in FIG. The research conducted by the present inventors has revealed that the diameter is 0.3 μm or less.

Note that the vertical axis in the figure indicates the mounting position of the plurality of magnetic disks 1 in the axial direction of the spindle motor 4 (one in order from the top).
．． 2, 3. ．． ．． , 8) and the upper and lower recording surfaces (A, B) of the magnetic disk 1 at each position. Also, the amount of deformation on the horizontal axis is determined by the servo heads 6 located in the center facing each other and the servo heads 6 facing each other. The amount of deformation in the radial direction of another magnetic disk 1 relative to the magnetic disk 1 on which a track is recorded, that is, the amount of off-track is shown.

For this reason, in order to cope with the increase in information recording density, the intervals between tracks provided concentrically on the magnetic disk 1 are several microns.
m or less, the magnetic disk 1 has a servo head 6 that reads position information and another magnetic head 5 that performs normal data recording/reproducing operations depending on temperature changes.
This eliminates positional deviation in the radial direction of the servo head 6.
Once the positioning on the target track is completed using the position information read from the magnetic head 5, off-track, where the actual position of the magnetic head 5 deviates from the target track, will no longer occur, improving operational reliability. will improve.

Further, in the case of this embodiment, the large diameter portion 46a of the inner hub 46 that is coupled to the outer hub 45 is provided at a position away from the mounting position of the permanent magnet 47 that constitutes the spindle motor 4, and the inner Since the hub 46 is made of a magnetic material, the negative magnetic influence from the permanent magnet 47 on the external magnetic disk 1 and the like is reduced.

Furthermore, an inner hub 46 coupled to an outer hub 45
Since the large diameter fm 46a is provided in a position away from the mounting position of the permanent magnet 47 constituting the spindle motor 4, thermal deformation of the permanent magnet 47 is caused by the side of the outer hub 45 holding the magnetic disk 1. Therefore, there is no need to take measures such as dividing the permanent magnet 47 in the circumferential direction to prevent this, reducing the number of parts and improving the ease of assembling the magnetic disk device.

Further, since the inner hub 46 and the outer hub 45 are made of iron-based material having the same coefficient of thermal expansion as the motor shaft 41, the outer ring is fixed to the inner hub 46 and the outer hub 45, and the inner ring is fixed to the motor shaft 41. Pressure fluctuations in the axial direction due to temperature changes are eliminated for the fixed bearings 44a and 44b,
The life of the bearings 44a and 44b is extended, and fluctuations in the rotational speed of the spindle motor 4 are eliminated, making it possible to realize stable operation.

Furthermore, by constructing the motor shaft 4l, outer hub 45, and inner hub 46 with similar materials,
Only one type of material needs to be handled by hand, contributing to improved productivity of magnetic disk drives.

[Embodiment 2] FIG. 4 is a sectional view showing an example of a main part of a magnetic disk device according to another embodiment of the present invention.

In the case of the second embodiment, a motor shaft 141 with one end protruding into the sealed space 8 is attached to a motor base 142 provided integrally with the base 11, and a pair of bearings 14
4a, and is rotatably supported via a bearing 144b.

A magnetic fluid seal 148 is provided inside the bear link l44a that supports the motor shaft 141 so as to surround the motor shaft 141, and prevents dust from entering the sealed space 8 from the outside through the space around the motor shaft 141. Prevents intrusion.

At the protruding end of the motor shaft 141 toward the closed space A side,
An outer hub 145 is coaxially fixed.

As in the case of the first embodiment, this outer hub 145 has a thinner wall surface on the outer periphery that holds the plurality of magnetic disks 1, and has a thinner wall surface on the outer periphery inside. The inner hub 146 has a reduced thickness,
They are inserted coaxially with a predetermined gap G over the entire circumference.

The outer hub 145 and the inner hub 146 are made of materials having the same coefficient of thermal expansion, and the insertion end of the inner hub 146 forms a large diameter section 146a, which is connected to the outer hub 145. There is a pressure pad on the inner edge of the rim. The inner hub 146 and the outer hub 145 are coaxially and integrally coupled with a gap G formed over almost the entire circumference and entire length by fixing by shrink fitting, adhesive, or the like.

A permanent magnet 1 is located at the center of the inner circumferential surface of the inner hub 146, that is, at a position away from the large diameter section 146a.
47 is fixed, and the motor shaft 141
A coil 143 that generates a rotating magnetic field is provided at a position surrounded by the permanent magnet 147 on the side of the motor base 142 that supports the motor base 142 . As a result, it is rotatably supported by the motor shaft 141, and has a structure in which rotational force is applied to the outer hub l45 and the inner hub 146, which hold a plurality of magnetic disks 1 (not shown).

A flange portion 145a is provided at the lower end of the outer hub 145.
is formed, and the magnetic disk 1 is stably held by pinching the magnetic disk 1 and disk spacer 2 (not shown) with a disk clamp 3 (not shown) that is locked on the upper end surface. .

A ring-shaped abutment member 149 having a convex cross-sectional shape on the side of the magnetic disk 1 is interposed between the flange portion 145a and the magnetic disk 1, and is arranged to provide a ring-shaped contact member 149 with a convex cross-sectional shape on the side of the magnetic disk 1. It has a structure in which it makes line contact around the outer hub 145 over the entire circumference.

In this way, in the case of the second embodiment, as well as in the case of the first embodiment, the inner hub 146 and the outer hub 145
Since both are made of materials with the same coefficient of thermal expansion, eccentricity due to temperature changes does not occur even if the joint between the two is processed more strictly than necessary. Since the thin outer hub 145 side deforms in response to the thermal deformation of the spacer 2 assembly in the axial direction, deformation of the magnetic disk 1 in the radial direction can be prevented.

Furthermore, since the contact member 149 provided on the flange portion 145a of the outer hub 145 is in line contact with the magnetic disk 1 in the circumferential direction of the outer hub 145,
Since the radial deformation of the outer hub 145 is absorbed by the tilting motion of the contact member 149 with the contact line portion as a fulcrum and is not transmitted to the magnetic disk 1, the occurrence of radial deformation of the magnetic disk 1 can be prevented.

[Embodiment 3] FIG. 5 and FIG. 6 are a cross-sectional view and a perspective view, respectively, showing an example of a main part of a magnetic disk device according to another embodiment of the present invention.

In the first and second embodiments, the wall thickness of the outer hub 45 and the outer hub 145 is thinned to intentionally lower the rigidity, but in the case of the third embodiment, the wall surface of the outer hub 245 is A plurality of notches 245b are formed at equal intervals in the circumferential direction, and a wall surface connects the upper end of the outer hub 245 to which the disc clamp 3 is fixed and the lower end where the flange 245a is formed. 24
By reducing the cross-sectional area of 5C, the outer hub 245
The rigidity in the axial direction of the magnetic disk 1 and the disk spacer 2 is intentionally made lower than that of the aggregate of the magnetic disk 1 and the disk spacer 2.

Further, the outer hub 245 is made of a material having the same coefficient of thermal expansion as the inner hub 246.

As a result, the same effects as in the first and second embodiments can be obtained in the third embodiment as well.

[Embodiment 4] In the embodiments 1 to 3, the outer knob 1b 45. which holds the magnetic disk 1 and the disk spacer 2. By making the rigidity of the outer hub 145 and the outer knob 245 smaller than the rigidity of the aggregate of the magnetic disk 1 and disk spacer 2, radial deformation of the magnetic disk 1 due to thermal expansion of both can be prevented. was prevented, but
In the case of the present embodiment 4, the material (thermal expansion coefficient) of the disk spacer 2 is different from that of the magnetic disk 1 and the outer knob 45.
, 145, and 245, thermal deformation of the magnetic disk 1 is prevented by optimizing the thermal expansion coefficients.

In other words, as shown in FIG. 1, the thickness of the disk spacer 2 is generally several times or more than the thickness of the magnetic disk 1, so the overall thickness of the magnetic disk 1 and disk spacer 2 is The thermal expansion coefficient can be considered to be almost the same as that of the disk spacer 2, and by making the thermal expansion coefficients of the disk spacer 2 and the outer hub 45, 145, 245 almost equal, the outer hub 45, 14
5.245 and the aggregate of the magnetic disk 1 and disk spacer 2 can be eliminated.

Note that from the viewpoint of actual production, the disc spacer 2 is replaced by the disc spacer 2 and the outer hub 45, 145, 24.
It is preferable to make it from the same material as 5.

For example, the magnetic disk 1 is made of aluminum with a thickness of 2 mm (coefficient of thermal expansion: 2 4 x 1 0 -'/t), and the disk spacer 2 is made of martensitic stainless steel with a thickness of 5 u (coefficient of thermal expansion: 1 0 x 1 0 ). -”/t), there are 8 magnetic disks l and 7 disk spacers 2.
In the case of a magnetic disk l and disk spacer 2, the coefficient of thermal expansion β in the axial direction of the spindle motor 4 is β = (2x8x (2 4xl O-”) +5x7
(1 0xi(1”))/(2x8+5x7)=
14.4X10-'/t.

If the outer hub 45, 145, 245 is made of iron-based material, its coefficient of thermal expansion is approximately 12X10-@/°C. The coefficient of thermal expansion is almost the same as that of the body.

This prevents the assembly of the magnetic disk 1 and the disk spacer 2 from generating thermal stress due to a large difference in thermal expansion coefficient with the outer hub 45, 145, 245, and causes thermal deformation in the radial direction of the magnetic disk 1. Effective in prevention.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the above-mentioned Examples, and it should be noted that various changes can be made without departing from the gist of the invention. Not even.

For example, motor shaft. The materials constituting the outer hub, inner hub, magnetic disk, disk spacer, etc. are not limited to those exemplified in each of the above-mentioned embodiments, but may be any materials whose thermal expansion coefficients are in accordance with the spirit of the present invention. Alternatively, other materials may be used.

Furthermore, the overall structure of the magnetic disk device is not limited to that exemplified in each of the embodiments described above.

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical inventions are briefly described below.

That is, the magnetic disk device according to the present invention includes a plurality of magnetic disks that function as storage media, a spindle motor that generates rotational force, and a part of the spindle motor that connects the plurality of magnetic disks at predetermined intervals. a hub that rotates while being held substantially coaxially; a spacer that is interposed between the adjacent magnetic disks and defines the interval between the magnetic disks; and a spacer that is attached to the end of the hub and that is a plurality of the magnetic disks. a disk clamp that fixes the disk to the hub by pressing the disk in the axial direction; a group of magnetic heads that are arranged to face the magnetic disk and perform at least one of recording and reproducing information on the magnetic disk; and the magnetic head. A magnetic disk drive comprising: a drive mechanism for positioning a group of magnetic disks in a radial direction; an outer hub that holds a magnetic disk; at least one gap is provided between the inner hub and the outer hub; the coefficients of thermal expansion of the inner hub and the outer hub are approximately equal; Since the structure has a rigidity lower than that of the magnetic disk and the spacer held by the outer hub, the processing and assembly of the inner hub and outer hub can be controlled without making the processing and assembly more rigorous than necessary. During the fluctuation, no distortion occurs that would change the concentricity of the joint between the two.

In addition, by making the wall surface of the outer hub thinner or forming cutouts to reduce its rigidity, the outer hub side deforms by following the thermal deformation of the magnetic disk supported between the outer hub and the disk. Therefore, distortion does not occur in the magnetic disk due to restraint of thermal deformation of the magnetic disk.

In addition, by making the spacer interposed between the plurality of magnetic disks W from a material having the same coefficient of thermal expansion as the hub, the coefficient of thermal expansion of the aggregate consisting of the spacer and the magnetic disks becomes almost equal to that of the hub side. Thermal deformation in the magnetic disk is alleviated.

In addition, the contact portions of the outer hub and the disk clamp with respect to the magnetic disk are connected to first and second lines having substantially the same coefficient of thermal expansion as the magnetic disk and having substantially coaxial and same diameter line contact with the magnetic disk. By using contact pieces, the force that tends to deform the magnetic disk in the radial direction, which is generated by thermal deformation of the outer hub and the disk clamp, is absorbed by the tilting of the first and second contact pieces. This is not transmitted to the magnetic disk, and deformation of the magnetic disk in the radial direction can be avoided.

This eliminates the deviation of the center of rotation of the magnetic disk due to fluctuations in environmental temperature, prevents off-track of the magnetic head that records/reproduces information on the rotating magnetic disk, and prevents the operation of the magnetic disk drive. reliability is improved.

In addition, by manufacturing the inner hub and outer hub from the same material as the shaft of the spindle motor that supports the inner hub and outer hub through the bearing, pressure fluctuations in the axial direction of the bearing due to temperature changes are eliminated. In addition to extending the life of the bearing, fluctuations in the rotational speed of the spindle motor are reduced, resulting in stable operation over a long period of time.

In addition, the inner hub and the outer hub are made of magnetic material, a gap is provided between the inner hub and the outer hub over the entire circumference, and the structure is such that the inner hub and the outer hub are connected at the large diameter portion of the insertion end of the outer hub. By doing so, the thermal deformation of the permanent magnet placed in the axial center of the inner hub will not be transmitted to the outer hub side, eliminating the need for measures such as dividing the permanent magnet in the circumferential direction, and reducing the number of parts. , the assembly work of the magnetic disk device is simplified.

Further, due to the shielding effect of the inner hub and the outer hub made of magnetic material, the negative magnetic influence of the permanent magnet in the inner hub is prevented from reaching the magnetic disk held by the outer hub.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the structure of the main part of a magnetic disk device that is an embodiment of the present invention, FIG. 2 is a cross-sectional view showing an example of the overall configuration, and FIG. 3 is a magnetic disk drive of this embodiment. FIG. 4 is a diagram showing an example of the operation of a disk device; FIG. 4 is a sectional view showing an example of the structure of a main part of a magnetic disk device according to another embodiment of the present invention; FIG. FIG. 6 is a sectional view showing an example of the structure of a main part of an example magnetic disk device, and FIG. 6 is a perspective view thereof. 1...Magnetic disk, 2...Cover 2...Disk spacer, 3...Disk clamp, 3a...
Inner clamp (holding piece), 3b... Outer clamp (second contact piece), 4... Spindle motor, 41
... Motor shaft, 42 ... Motor base, 43
...Coil, 44a, 44b...Bearing, 45
...Outer hub, 45a...Flange part, 46.
... Inner hub, 46a... Large diameter portion, 47... Permanent magnet, 48a. 48b...magnetic fluid seal mechanism, 4
9... Contact member (l-th contact piece), 5... Magnetic head, 5a... Head arm, 5b... Leaf spring, 6...
...Servo head, 7...Head spacer, VCM1
...Voice coil motor, 8...Voice coil, 8a
...Coil frame, 9...Fixed! , 1 0...
Head clamp, 11...Base, 12...Pivot shaft, l3...Hub carriage, 13a...Flange portion, 14...Cover 15...Patch, l6
...High performance filter, 16a...Communication hole, 17...
- Control board, 18. ,19.20.21...Screw, 1
41...Motor shaft, 142...Motor base, 143...Coil, 144a...Bearing, l
44b...bearing, 145...outer hub,
145a...Flange part, 146...Inner hub, 146a...Large diameter part, 147...Permanent magnet, 14
8... Magnetic fluid seal, 149... Contact member (first
contact piece), 245...outer hub, 245a...
・Flange part, 245b...notch part, 245C・
... Wall surface, 246 ... Inner hub, A ... Closed space, G ... Gap between inner hub and outer hub.

Claims (1)

[Claims] 1. A plurality of magnetic disks that function as storage media, a spindle motor that generates rotational force, and a plurality of magnetic disks that form part of the spindle motor and are arranged substantially coaxially at predetermined intervals. a hub that holds and rotates; a spacer that is interposed between the adjacent magnetic disks and defines the interval between the magnetic disks; and a spacer that is attached to an end of the hub and that rotates the plurality of magnetic disks in the axial direction a disk clamp that is fixed to the hub by pressing on the magnetic disk; a magnetic head group that is arranged to face the magnetic disk and performs at least one of recording and reproducing information on the magnetic disk; A magnetic disk device comprising a drive mechanism that performs a positioning operation in the radial direction of a magnetic disk, wherein the hub includes an inner hub that holds a permanent magnet on its inner circumference, and a plurality of the magnetic disks on its outer circumference. and an outer hub for holding, at least one gap is provided between the inner hub and the outer hub, the coefficient of thermal expansion of the inner hub and the outer hub are approximately equal, and the rigidity of the outer hub is the same as that of the outer hub. A magnetic disk device characterized in that the rigidity is lower than that of the magnetic disk and the spacer held by an outer hub. 2. The outer diameter of the inner hub is smaller than the inner diameter of the outer hub, and the inner hub is coupled to the outer hub by a large diameter portion provided at an insertion end of the inner hub with respect to the outer hub. 2. The magnetic disk drive according to claim 1, wherein the gap is formed over substantially the entire circumference and entire length of the inner hub. 3. Claim 1, wherein the inner hub, the outer hub, and the spacer are made of the same magnetic material.
or the magnetic disk device described in 2. 4. The rigidity of the outer hub is set to a desired value by forming notches of a desired size at approximately equal intervals in the circumferential direction on the wall surface of the outer hub. The magnetic disk device according to claim 1, 2 or 3. 5. One end of the outer hub forms a flange portion that supports the plurality of magnetic disks, and a space between this flange portion and the magnetic disk located at the end has a coefficient of thermal expansion equivalent to that of the magnetic disk. 3. A first contact piece having a convex cross section and making a circular line contact with the magnetic disk is interposed around the outer hub. or the magnetic disk device described in 4. 6. The disk clamp is supported on a side of the outer hub and is interposed between a holding piece having approximately the same coefficient of thermal expansion as the outer hub, and the holding piece and the magnetic disk located at the outermost end. , a second contact piece having a coefficient of thermal expansion equivalent to that of the magnetic disk, having a convex cross section, and making a circular line contact with the magnetic disk around the outer hub and having approximately the same diameter as the first contact piece; Claim 1, 2, 3, 4 or 5, characterized in that it consists of a contact piece of
The magnetic disk device described. 7. The spindle motor supports the inner hub and the outer hub via bearings, and
Equipped with a stationary shaft to which a coil that generates a rotating magnetic field is fixed,
7. The magnetic disk drive according to claim 1, wherein the coefficient of thermal expansion of the stationary shaft, the inner hub, and the outer hub are approximately equal.