JPH06259913A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent the destruction of data and damage of a magnetic disk caused by a contact between a head and a disk by moving a flexure supporting member in directions for supporting the flexure and releasing its support so that the magnetic head is floated from a magnetic disk by a loading/unloading mechanism. CONSTITUTION:A magnetic head 3 is floated over a disk 4 keeping a slight space during the rotation of the disk 4. At this time, a flexure supporting member 61 is rotated around a supporting section 63 and displaced by an actuator 64 so as not to touch the projecting part of the bent part 25 of a suspension 2. At the time of unloading, the actuator 64 is actuated, the member 61 is moved while slidingly touching the bending part 25 of the suspension 2 and after the head 3 is moved away from the disk 4, it is retreated to a part outside the area of the disk 4, and the loading is carried out vice versa. Thus, the contact between the magnetic head and the magnetic disk at the time of loading is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device having a magnetic head load / unload mechanism.

[0002]

2. Description of the Related Art First, a conventional small magnetic disk device used as an external storage device of a laptop computer will be described with reference to the drawings.

FIG. 7 is a perspective view of a conventional magnetic disk device. A magnetic disk 4 fixed to a spindle motor (not shown) is provided on the base 1. Reference numeral 5 denotes a magnetic head support mechanism, which is configured as follows. 5
Reference numeral 1 denotes an arm, and the arm 51 is rotatably supported by a bearing shaft unit 52. Reference numeral 53 is a coil portion, 54 is an upper yoke, 55 is a lower yoke, and 56 is a permanent magnet. The upper yoke 54, the lower yoke 55 and the permanent magnet 56 constitute a magnetic circuit. Coil part 53
A magnetic flux is generated in the portion where is located, and the arm 51 is rotated in the horizontal direction by passing a current through the coil portion 53. A magnetic head 3 is supported by the tip of the suspension 2 fixed to the arm 51. When a current is applied to the coil portion 53, the suspension 2 horizontally rotates about the bearing shaft unit 52, and the magnetic head 3 moves on the magnetic disk 4 in the radial direction. The magnetic head 3 is controlled to be located on a predetermined data track by a servo signal intermittently recorded on the data track of the magnetic disk 4.

Next, the structure of the suspension 2 will be described.
FIG. 8 is a perspective view of a suspension of a conventional magnetic disk device. In FIG. 8, reference numeral 21 is a flexure composed of a leaf spring, and bent portions 24 are provided on both sides of the flexure 21. Reference numeral 23 is a fixed part, and the arm 5
It is fixed to 1 by caulking or the like. 22 is a gimbal provided at the tip of the flexure 21 and is made of a thin metal plate. The magnetic head 3 is fixed to the gimbal 22, and a levitation rail is provided on the surface facing the magnetic disk so that the magnetic head 4 floats with a slight gap as the magnetic disk 4 rotates. Reference numeral 31 is a magnetic head portion provided with a gap portion for reading and writing data, and the magnetic head portion 31 is provided with a winding 32. 33 is winding 32
The winding tube 33 is a winding tube for protecting the winding wire 33, and the winding tube 33 is caulked and fixed to the bending portion 24 and the fixing portion 23.

In recent years, in order to achieve high capacity, the gap (flying height) between the magnetic head 3 and the magnetic disk 4 has become very small, and the flying rail of the magnetic head 3 and the surface of the magnetic disk 4 have become very flat. Has been done. Magnetic head 3
Recently, in order to avoid the attraction and abrasion between the magnetic disk 4 and the magnetic disk 4, many magnetic disk devices have a load / unload mechanism for using the method of floating the magnetic head 3 on the magnetic disk 4 by load / unload. There is.

FIG. 9 is a perspective view of a conventional magnetic disk device, which is equipped with a load / unload mechanism. In FIG. 9, reference numeral 7 denotes a load / unload mechanism provided on the outer circumference of the magnetic disk 4, and the load / unload mechanism 7 is provided with a flexure support member 71 for each suspension 2. Such a load / unload mechanism 7
A load / unload operation of the magnetic disk device having the above will be described with reference to FIGS. 10 (a), (b), and (c).

FIGS. 10A, 10B, and 10C are side views showing the load / unload operation of the conventional magnetic disk device, in which the magnetic head 3 surrounds the load / unload mechanism 7.
It is seen from the side where the winding is applied. First, the unload operation will be described. In FIG. 10A, the magnetic head 3 is floating above the magnetic disk 4 and is in a state capable of recording and reproducing data. When the predetermined recording / reproducing operation is completed, the magnetic head 3 is moved to the outer peripheral side of the magnetic disk 4. Then, the flexure 21 of the suspension 2 rides on the flexure support member 71, the suspension 2 is displaced in the direction away from the magnetic disk 4, and the magnetic head 3 separates from the magnetic disk 4 as shown in FIG. When the magnetic head 3 is further moved to the outer peripheral side, the magnetic head 3 is completely separated from the area of the magnetic disk 4, and the magnetic head 3 is moved to the position shown in FIG.
The unload operation is completed when the position comes to. On the other hand, the load operation is performed in the reverse process of the unload operation. That is, when the magnetic disk 4 rotates, the magnetic head 3 is moved to the area of the magnetic disk 4 (FIG. 10B). The magnetic head 3 gradually approaches the magnetic disk 4, and the flexure 21 of the suspension 2 is displaced so as to slide down from the flexure support member 71, so that the magnetic head 3 moves.
Will surface. In the magnetic disk device having such a load / unload mechanism 7, the magnetic head 3 always performs the load / unload operation on the outer peripheral side.

[0008]

The magnetic disk device is being miniaturized along with high capacity and high speed access, and the track width of the magnetic head 3 which is the recording width of data for achieving high capacity is very small. In order to achieve high-speed access, the acceleration applied to the suspension 2 is also increasing. In the conventional suspension 2, the suspension 2 is driven by the acceleration applied in the moving direction of the magnetic head 3.
Vibration occurs, and it takes time until the vibration is dampened, so that the positioning time cannot be shortened, and if the amplitude of the resonance of the suspension 2 is large or the frequency is low, the servo band cannot be wide and a disturbance occurs. Of the magnetic disk 4 due to the problem of being off the track of
There is a problem of contacting with, which has been a problem for achieving high-speed access.

Since the magnetic disk device is mounted on a laptop computer or the like, the size of the magnetic disk device 4 has been reduced, and the outer diameter of the magnetic disk 4 has been increased from the conventional 3.5 inch size to 2.5 inch. It has come up to the size of 8 inches. When considering a load / unload operation, particularly a load operation, on a small-diameter disk such as a 1.8-inch size, the non-contact between the magnetic head 3 and the magnetic disk 4 during the loading is a normal phenomenon that occurs in the magnetic head 3 during the loading. It has been found to be achieved by pressure, and for small diameter discs the linear velocity in the load area is small,
Further, since the size of the magnetic head 3 is becoming smaller due to the miniaturization, the positive pressure generated at the time of loading is very small, and it becomes difficult to float the magnetic head 3 on the magnetic disk 4 in a non-contact manner. ing. Further, the position where the load / unload operation is performed is fixed to the outer peripheral side.

Generally, in a magnetic disk device, the data recording / reproducing characteristics are better on the outer peripheral side of the magnetic disk 4.
On the inner circumference side, the deterioration of the reproduction output due to the small linear velocity,
There is an area that cannot be used because there is a variation in reproduction output that occurs due to distortion or the like caused by fixing to the spindle motor, and the data area is configured to be used up to the outer periphery as much as possible in order to increase the recording capacity. Therefore, data is also recorded in the load / unload area, and the magnetic disk 4 may be damaged by long-time load / unload operation to destroy the data. Therefore, there is also proposed a magnetic disk device in which the load / unload mechanism 7 as in the conventional example is provided on the inner peripheral side of the magnetic disk 4 and the load / unload is performed on the inner peripheral side. However, in such a magnetic disk device, since the magnetic head 3 is always supported on the magnetic disk 4 when the magnetic disk 4 is stopped, the magnetic head 3 and the magnetic disk 3 are supported when a large impact is applied. There is a high risk that the magnetic head 3 will come into contact with the magnetic head 4 and damage the magnetic gap of the magnetic head 3.

Further, since the small magnetic disk device mounted on the laptop computer is often carried around, it is necessary to consider impact and the like. A magnetic disk device that does not have a mechanism for retracting the magnetic head 3 to the outside of the area of the magnetic disk 4 when the disk 4 is stopped has a small permissible amount of impact, and when a large impact is applied, the magnetic head 3 and the magnetic disk 4 are There is a risk of contact with the magnetic head 3 and damage to the data, which requires careful handling by the user carrying the laptop computer.

Therefore, the present invention solves the above-mentioned problems of the prior art. It is possible to load and unload regardless of the position on the magnetic disk, and even if there is contact between the magnetic head and the magnetic disk during the loading operation. Provides a magnetic disk device that has no risk of destroying data, no risk of damaging the magnetic head even if shock is applied at the time of stop, and can immediately unload the magnetic head when disturbance such as shock occurs during use The purpose is to do. It is another object of the present invention to provide a magnetic disk device including a suspension that suppresses vibration caused by acceleration during positioning and enables high-speed positioning.

[0013]

To this end, the magnetic disk device of the present invention extends the flexure by extending the load / unload mechanism of the magnetic head onto the magnetic disk so as to intersect the flexure of the suspension holding the magnetic head. A flexure support member for floating the magnetic head above the magnetic disk by supporting the magnetic head, and moving means for moving the flexure support member in a direction for supporting the flexure and a direction for releasing the support. Further, the flexure is partially cut and raised to form a bent portion, and the flexure support member is slidably contacted below the bent portion.

[0014]

According to the above structure, at least the load / unload operation is possible in the magnetic head movable area on the magnetic disk. Therefore, normally, the load / unload operation is performed at the innermost circumference of the magnetic disk on which no data is recorded. After unloading, it is possible to retract the magnetic head outside the area of the magnetic disk, and the contact between the magnetic head and the magnetic disk at the time of loading, which is a problem in the magnetic disk device using a small diameter magnetic disk It is possible to prevent the data from being destroyed, and the risk of the magnetic head and the magnetic disk coming into contact with each other due to a shock during carrying. Furthermore, when a disturbance such as a shock occurs during operation, the magnetic head can be immediately unloaded at the flying position, so that data destruction due to contact between the magnetic head and the magnetic disk can be minimized. In addition, since the flexure of the suspension is partially cut and raised to form the bent portion, the rigidity in the torsional direction can be increased without increasing the weight of the suspension, so that the amplitude of vibration generated by the acceleration applied at the time of access can be increased. It can be kept small, and the resonance frequency of vibration can be increased. Therefore, it is possible to solve problems such as contact between the magnetic head and the magnetic disk, shorten the vibration settling time during positioning, and increase the servo band. Become.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a suspension of a magnetic disk device according to an embodiment of the present invention. In FIG. 1, the suspension 2 is configured as follows. Bending portions 24 are provided on both sides of the flexure 21 formed of a leaf spring. The flexure 21 is joined to the fixing portion 23 by welding or the like so as to be fixed to the arm. A thin plate-shaped gimbal 22 is fixed to the tip of the flexure 21, and the magnetic head 3 is fixed to the gimbal 22. A magnetic head portion 31 having a magnetic gap for recording / reproducing data is provided at the rear end portion of the magnetic head 3, and a winding 32 is wound around the magnetic head portion 31. The winding 32 is protected by a winding tube 33 and is fixed by being caulked to the bending portion 24 and the fixing portion 23 of the flexure 21.

A levitation rail is provided on the surface of the magnetic head 3 facing the magnetic disk, and the magnetic head 3 generated on the levitation rail by the rotation of the magnetic disk 4 (see FIG. 2) is moved away from the magnetic disk 4. The positive pressure that acts and the magnetic head 3 near the fixed portion 23 of the flexure 21
Balances with the restoring force generated by the bending of the magnetic disk 4 toward the magnetic disk 4 and floats above the magnetic disk 4 with a minute gap. 25 is a flexure 21
Is a bent portion formed by partially cutting and raising a plane portion sandwiched by the bent portions 24, and is slightly inclined, and the bent portion 25 is provided with a protruding portion 26 in its length direction. .

The suspension 2 is generally a magnetic disk 4.
The magnetic head 3 is positioned by rotating the magnetic head 3 in the radial direction. The acceleration applied in the moving direction has also become very large with the recent increase in access speed.
When such an acceleration is applied in the width direction of the suspension 2, the flexure 21 generates a vibration such that the flexure 21 is twisted at the flat portion sandwiched by the bent portions 24. This vibration occurs because the rigidity of the plane portion sandwiched by the bent portions 24 in the twisting direction is low. However, by providing the bent portion 25 on the flat portion sandwiched by the bent portions 24, the rigidity in the twisting direction can be increased. Moreover, since no other member is attached to increase the rigidity, the weight of the suspension 2 does not increase. As a result, the amplitude of the torsional vibration of the suspension 2 that has been conventionally generated can be suppressed to a low level, and the vibration frequency can be increased.

Next, the magnetic disk device will be described with reference to FIGS.
Will be explained. FIG. 2 is a perspective view of a magnetic disk device according to an embodiment of the present invention. In FIG. 2, 1 is a base and 4 is a magnetic disk fixed to a spindle motor (not shown). Reference numeral 5 denotes a magnetic head support mechanism, which is configured as follows. Reference numeral 51 is an arm, and the arm 51 is rotatably supported by a bearing shaft unit 52. Reference numeral 53 is a coil portion, 54 is an upper yoke, 55 is a lower yoke, and 56 is a permanent magnet. The upper yoke 54, the lower yoke 55 and the permanent magnet 56 constitute a magnetic circuit. A magnetic flux is generated in the portion where the coil portion 53 is located, and when a current is passed through the coil portion 53, a magnetic force is generated in the coil portion 53 so that the arm 51 moves in the horizontal direction.

The magnetic head 3 is supported by the tip of the suspension 2 fixed to the arm 51 so that it can move on the magnetic disk 4. The positioning of the magnetic head 3 is controlled so as to be positioned at a predetermined data track by a servo signal intermittently recorded on the data track of the magnetic disk 4. The suspension 2 used in this embodiment is the one shown in FIG. 1, and a bending portion 25 having a protruding portion 26 is provided on a plane portion sandwiched by the bending portions 24 of the flexure 2.

In FIG. 2, the load / unload mechanism 6 is constructed as follows. 61 is suspension 2
At least one flexure supporting member is provided for the magnetic disk 4 and is movable in a crossing direction substantially orthogonal to the suspension 2.
Supported by 3. Reference numeral 64 denotes an actuator for rotating the flexure support member 61 in the horizontal direction, and an electromagnetic solenoid is used in this embodiment. In the load / unload method, the magnetic head 3 is loaded / unloaded on the inner peripheral side of the magnetic disk 4 in a normal state, and the magnetic head 3 is retracted to the outside of the area of the magnetic disk 4 after the unloading.

Next, the load / unload operation of the magnetic disk device will be described with reference to FIGS. 3 (a), 3 (b) and 3 (c) and FIGS. 4 (a), 4 (b) and 4 (c). 3 is a plan view showing a load / unload operation of the magnetic disk device according to the embodiment of the present invention, and FIG. 4 is a side view showing a load / unload operation of the magnetic disk device according to the embodiment of the present invention. is there. 3A corresponds to FIG. 4A, FIG. 3B corresponds to FIG. 4B, and FIG. 3C corresponds to FIG. 4C. First, the unload operation will be described.

FIGS. 3A and 4A show a state in which the magnetic head 3 is floating above the magnetic disk 4 with a slight gap left between them.
You can move freely on the recording surface of. At this time, the flexure support member 61 has the protrusion 2 of the bending portion 25 of the suspension 2.
The actuator 64 rotates and displaces the support portion 63 as a center so as not to come into contact with the actuator 6. In FIGS. 3B and 4B, when the actuator 64 is moved, the flexure support member 61 moves while slidingly contacting the protruding portion 26 of the bending portion 25 of the suspension 2. At this time, the bent portion 25 of the suspension 2 is slidably contacted with the flexure support member 61 and displaced so as to ride on the flexure support member 61, and the magnetic head 3 is separated from the magnetic disk 4. Flexure support member 6
When 1 is completely displaced, the unloading operation of the magnetic head 3 is completed.

Thereafter, the suspension 2 is supported by the flexure support member 61 and moved to a position outside the area of the magnetic disk 4 while the magnetic head 3 is separated from the magnetic disk 4, as shown in FIG. 4 (c)
Will be retracted to the position. The reason why the protruding portion 26 is provided on the bent portion 25 is to increase the strength of the bent portion 25 and to reduce the contact resistance with the flexure supporting member 61 to smoothly perform load / unload.

FIG. 5 is a plan view of the main part of the magnetic disk device according to the embodiment of the present invention. In FIG. 5, 62
Is a wide portion that is formed on the base end side of the flexure support member 61 and has a width wider than that. In the vicinity of the retracted magnetic head 3, the bent portion 25 of the suspension 2 is extended to the wide portion 62 of the flexure support member 61. Contacted and supported.
The reason why the wide portion 62 is provided on the flexure support member 61 will be described later. The load operation is performed in the reverse manner of the unload operation described above. That is, when the magnetic disk 4 is stopped, the magnetic head 3 is moved by the bending portion 25 of the suspension 2 and the flexure supporting member 61.
Are saved out of the area ((c) of FIG. 3 and (c) of FIG. 4). When the magnetic disk 4 rotates, the suspension 2 is moved to the inner peripheral side of the magnetic disk 4 while supporting it ((b) of FIG. 3 and (b) of FIG. 4), and the flexure support member 61 is displaced by the actuator 64. The bent portion 25 of the suspension 2 is separated from the flexure support member 61, and the magnetic head 3 is levitated on the magnetic disk 4 and the loading operation is completed ((a) of FIG. 3 and (a) of FIG. 4).

The configuration of the load / unload mechanism 6 will be described in more detail. The suspension 2 is supported by the wide portion 62 of the flexure support member 61 and is supported outside the region of the magnetic disk 4. Flexure support device 61
The shape of the portion of the suspension 2 that first comes into contact with the bent portion 25 is an arc shape with the center of the bearing shaft unit 52 that rotatably supports the arm 51 as the center, and the radius of this arc is Letting R be L and the distance from the center of the bearing shaft unit 52 to the substantially center of the bending portion 25 of the suspension 2 in the longitudinal direction, there is a relation of approximately L = R. In addition, the flexure support member 6
By forming the shape of 1 in this way, the suspension 2 is supported by the flexure supporting member 61, that is, the magnetic head 3 is separated from the magnetic disk 4, and the magnetic disk 4 on the inner or outer circumference of the magnetic disk 4 is formed. You are free to move outside the area.

The wide portion 6 of the flexure support member 61 is also provided.
When the suspension 2 is supported by the suspension 2, the suspension 2 does not separate from the flexure support member 61 even when the actuator 64 is moved to displace the flexure support member 61. The reason for such a configuration will be described with reference to FIGS. 3A and 6A and 6B, which are partially enlarged views showing the load / unload operation of the magnetic disk device in the embodiment of the present invention. .

When the magnetic head 3 freely moves on the magnetic disk 4 to perform the recording / reproducing operation, the flexure support member 61 is displaced by the actuator 64 as shown in FIG. At this time, the magnetic head 3 is positioned on a predetermined data track by the servo signal recorded on the magnetic disk 4 to perform recording / reproduction. However, if control is lost for some reason such as disturbance, the magnetic head 3 may run away. When the direction of runaway is on the inner circumference side, it collides with an inner circumference stopper member (not shown) and stops, but when it is on the outer circumference side, the magnetic head 3 jumps out of the area of the magnetic disk 4. .

Therefore, even if the wide portion 62 is provided on the flexure support member 61 and the magnetic head 3 can move the magnetic disk 4 freely, when the magnetic head 3 comes to the outermost peripheral side, the bent portion 25 of the suspension 2 is formed. Is slid on the wide portion 62 of the flexure support member 61, and when the magnetic head 3 runs away to the outer peripheral side of the magnetic disk 4, before the magnetic head 3 comes out of the area of the magnetic disk 4,
The wide portion 62 of the flexure support member 61 and the bent portion 25 are brought into sliding contact with each other to lift the suspension 2 and separate the magnetic head 3 from the magnetic disk 4 to be in a normal retracted state. An outer peripheral stopper member (not shown) is provided so as not to move further from the retracted position in the direction away from the magnetic disk 4.

With the above configuration, the magnetic head 3 can be unloaded at any position on the magnetic disk 4. Next, the unload operation when a disturbance such as a shock occurs in the magnetic disk device will be described. In this embodiment, a piezoelectric element (not shown) is provided inside the magnetic disk device as a disturbance detector that detects an external impact. The disturbance detector may be any one capable of detecting acceleration such as impact or vibration. When the output of the disturbance detector in which a disturbance occurs during operation exceeds a predetermined level, the actuator 64 is immediately moved to unload the magnetic head 3 regardless of the position of the magnetic head 3. is doing. Therefore, even if disturbance occurs, data destruction due to contact between the magnetic head 3 and the magnetic disk 4 can be avoided. Further, when the output of the disturbance detector exceeds a predetermined level, the magnetic head 3 may be moved to the outer peripheral side and the wide portion 62 of the flexure support member 61 may unload the magnetic head 3. It is also effective to carry out the above two methods at the same time.

[0031]

As described above, according to the magnetic disk device of the present invention, at least the load / unload operation is possible in the magnetic head movable area on the magnetic disk, and normally, the maximum amount of the magnetic disk on which no data is recorded is recorded. By performing loading / unloading on the inner circumference and retreating the magnetic head to the outside of the magnetic disk area after unloading, the magnetic head at the time of loading, which is a problem in a magnetic disk device using a small-diameter magnetic disk, It is possible to avoid the data destruction caused by the contact of the magnetic disk, and the risk of the magnetic head and the magnetic disk coming into contact with each other due to the impact during carrying is eliminated. Furthermore, when a disturbance such as a shock occurs during operation, the magnetic head can be immediately unloaded at the flying position, so that data destruction due to contact between the magnetic head and the magnetic disk can be minimized. In addition, since the flexure of the suspension is partially cut and raised to form the bent portion, the rigidity in the torsional direction can be increased without increasing the weight of the suspension, so that the amplitude of vibration generated by the acceleration applied at the time of access can be increased. It can be kept small, and the resonance frequency of vibration can be increased. Therefore, it is possible to solve problems such as contact between the magnetic head and the magnetic disk, shorten the vibration settling time during positioning, and increase the servo band. Become.

[Brief description of drawings]

FIG. 1 is a perspective view of a suspension of a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a perspective view of a magnetic disk device according to an embodiment of the present invention.

FIG. 3 is a plan view showing a load / unload operation of the magnetic disk device according to the embodiment of the present invention.

FIG. 4 is a side view showing a load / unload operation of the magnetic disk device according to the embodiment of the present invention.

FIG. 5 is a plan view of a main part of a magnetic disk device according to an embodiment of the present invention.

FIG. 6 is a partially enlarged view showing a load / unload operation of the magnetic disk device according to the embodiment of the present invention.

FIG. 7 is a perspective view of a conventional magnetic disk device.

FIG. 8 is a perspective view of a suspension of a conventional magnetic disk device.

FIG. 9 is a perspective view of a conventional magnetic disk device.

FIG. 10 is a side view showing a load / unload operation of a conventional magnetic disk device.

[Explanation of symbols]

 2 suspension 3 magnetic head 4 magnetic disk 5 magnetic head support mechanism 6 load unload mechanism 21 flexure 25 bending part 53 coil part 61 flexure support member 62 wide part 64 actuator

Claims (3)

[Claims] 1. A magnetic head support mechanism comprising: a suspension having a flexure for holding a magnetic head; and a rotation driving means for rotating the flexure horizontally to move the magnetic head in a radial direction of a magnetic disk, and A magnetic disk device comprising a load / unload mechanism for loading / unloading the magnetic head to / from the disk, wherein the load / unload mechanism extends onto the magnetic disk so as to intersect with the flexure, and the flexure A flexure supporting member for floating the magnetic head above the magnetic disk by supporting the flexure, and a moving means for moving the flexure supporting member in a direction of supporting the flexure and a direction of releasing the flexure. Magnetic disk drive. 2. The magnetic disk according to claim 1, wherein the flexure is partially cut and raised to form a bent portion, and the flexure supporting member is slidably contacted below the bent portion. apparatus. 3. The flexure support member has an arcuate planar shape and has a wide portion at a base end thereof, and the bent portion is slid on the wide portion to cause the magnetic field of the magnetic head to move. 3. The magnetic disk device according to claim 2, wherein the magnetic disk device is unloaded from the disk.