JPH04319583A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prolong the service life of a medium by shifting an area where a magnetic disk touches a disk medium everytime a coincident signal is sent out by a comparing device repeating the operations of contact/start/stop with the disk medium in accordance with the rotational stop of the disk medium. CONSTITUTION:When a magnetic head 3 is returned to a contact/start/ stop CSS area, its distance is calculated at a control circuit 8 which receives a coincident signal by regulating an offsetting quantity equivalent to the sliding width of the magnetic head 3 from the current position of the magnetic head 3 to the CSS area used so far and sent to a servo circuit 9. Based on the distance given from the control circuit 8, a servo signal is sent to a power amplifier 10 so as to move the the distance whose offsetting quantity is regulated. Then, a carriage 12 is stopped at a new CSS area moved as much as the width of a slider by the power amplifier 10 so as to supply a current corresponding to this servo signal to a motor 11.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a magnetic disk that performs a contact start/stop (hereinafter abbreviated as CSS) operation in which a magnetic head floats as the disk medium rotates and comes into contact with the disk medium when the disk medium stops rotating. The present invention relates to devices, and particularly to a magnetic disk device that extends the life of a disk medium and prevents a magnetic head from being attracted to the surface of the disk medium.

In recent years, in magnetic disk drives, in response to demands for faster access speeds and higher recording densities, advances have been made in reducing the flying height of magnetic heads, smoothing disk media, and thinning magnetic layers and protective films. ing.

[0003] As the seek speed increases, flying stability of the magnetic head is strongly required. by the way,
In a magnetic disk device that performs CSS operation, the magnetic head is in contact with the protective film when the disk medium starts rotating.
The slider and the protective film rub against each other until it floats, and before the disk medium stops, the magnetic head contacts the protective film and the slider and protective film rub against each other in the same way, but this shortens the life of the disk medium. In addition, it is necessary that the magnetic head is not attracted to the protective film and that it becomes difficult to start the motor that rotates the disk medium.

0004

[Prior Art] In a conventional magnetic disk device, a CSS area is defined on the disk medium, and when the power is turned off,
The magnetic head was always moved to this CSS area.

[0005] Therefore, the magnetic head and disk medium are
When performing CSS operations, always touch in this CSS area,
There was a reconciliation going on.

[0006]

[Problem to be solved by the invention] As mentioned above, conventionally C
Since rubbing with the magnetic head takes place in the SS area,
The thinner the protective film is, the lower its durability is, and the problem frequently arises that the slider of the magnetic head is attracted to the smoothed surface of the protective film.

To avoid this, for example, the magnetic head is left floating when the power is turned off, or the magnetic head is moved out of the area of the disk medium so that the magnetic head is not forcibly brought into contact with the disk medium. Loading/unloading mechanisms have been devised, but magnetic disk drives have become expensive and the spacing between the facing surfaces of the multiple discs that make up the disk media has become narrower to increase capacity. /It is difficult to use the unloading mechanism.

In particular, this method cannot be used in a small, high-capacity magnetic disk device, so it shortens the life of the disk medium, and the magnetic head is attracted to the protective film smoothed by the CSS operation. There is a problem in that it is difficult to start the motor that rotates the disk medium.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide a magnetic disk device that improves the durability of the disk medium and prevents the magnetic head from being attracted to the disk medium.

0010

Means for Solving the Problems FIG. 1 is a block diagram illustrating the principle of the present invention. The detection means 2 detects contact or separation between the magnetic head 3 and the disk medium 4 and notifies the storage means 6 of the contact or separation. The storage means 6 reads and stores the number of revolutions of the disk medium 4 from the motor 5 that rotates the disk medium 4 each time the detection means 2 detects contact or separation between the magnetic head 3 and the disk medium 4.

The comparison means 7 sends a coincidence signal to the servo means 1 when the number of rotations stored in the storage means 6 becomes equal to or less than a preset number of rotations. The servo means 1 shifts the area where the magnetic head 3 contacts the disk medium 4 when the comparison means 7 sends out a coincidence signal.

That is, each time the CSS operation is repeated and the comparison means 7 sends out a coincidence signal, the CSS area where the magnetic head 3 contacts the disk medium 4 is shifted. When shifting this CSS area, the servo means 1 The width of the slider is sequentially moved from the inner circumferential side to the outer circumferential side of the disk medium 4 or from the outer circumferential side to the inner circumferential side.

[0013]

[Operation] With the above structure, when the magnetic head 3 collides with a convex portion on the surface of the disk medium 4 and vibrates, the detection means 2 detects this vibration and notifies the storage means 6 of the vibration.

When the convex portion of the protective film of the disk medium 4 is scraped and smoothed by the CSS operation of the magnetic head 3 and the magnetic head 3 is about to be attracted to the disk medium 4, the comparing means 7 detects the servo means 1. The servo means 1 moves the CSS area in order to send out a coincidence signal. Therefore, the magnetic head 3 is not attracted to the disk medium 4.

[0015] Then, before the thin protective film is destroyed, the CS
Since the S area is moved, the durability of the disk medium 4 can be improved.

[0016]

Embodiment FIG. 2 is a block diagram of a circuit showing one embodiment of the present invention. When the power is turned on, the control circuit 8 controls the motor drive circuit 19 to supply a drive current to the motor 5 and rotate the motor 5.

Therefore, the disk 17 constituting the disk medium
and 18 rotate, and the magnetic head 3 attached to the tip of the arm of the carriage 12 floats against the pressure of the mounting spring due to the wind pressure accompanying the rotation of the disks 17 and 18.

Since the motor 5 rotates at a constant speed, the number of rotations is sent to the motor drive circuit 19, and this number of rotations is also sent to the discrimination circuit 21 and memory 22. The magnetic head 3 has
For example, AE (Acoustic Emission)
Elements 13 to 16 are installed respectively, and AE element 1
3, the magnetic head 3 that accesses the top surface of the disk 17 collides with the convex portion of the protective film and vibrates while in contact with the top surface of the disk 17. As is well known, this vibration is converted into an electrical signal and sent to the A/D conversion circuit 20.

Further, the AE element 14 vibrates as the magnetic head 3 accessing the lower surface of the disk 17 collides with the convex portion of the protective film while in contact with the lower surface of the disk 17. It is converted into an electrical signal and sent to the A/D conversion circuit 20.

Furthermore, the AE element 15 vibrates when the magnetic head 3 accessing the top surface of the disk 18 collides with the convex portion of the protective film while in contact with the top surface of the disk 18. Convert it into an electrical signal and send it to the A/D conversion circuit 20,
The E element 16 vibrates when the magnetic head 3 that accesses the lower surface of the disk 18 collides with the convex portion of the protective film while in contact with the lower surface of the disk 18, and converts this vibration into an electrical signal. ,
The signal is sent to the A/D conversion circuit 20.

Therefore, the A/D conversion circuit 20 sends to the discrimination circuit 21 a digital value corresponding to the level of the electric signal sent out by each AE element 13 to 16. FIG. 3 is a diagram illustrating the relationship between AE output and rotation speed.

Taking the AE output on the vertical axis and the rotation speed of the motor 5 on the horizontal axis, when the rotation speed of the motor 5 is 0, the AE output is also 0. As the rotation speed of the motor 5 increases, the AE output also increases, and when the CSS operation of the magnetic head 3 is the first time, it reaches a maximum at a certain rotation speed, as shown in ■, and when the rotation speed increases beyond that. , as the magnetic head 3 levitates,
The vibration of the magnetic head 3 also becomes smaller, and the AE output gradually decreases.

When the rotational speed reaches a, the magnetic head 3 flies higher than the protrusions of the disks 17 and 18, so the vibration of the collision subsides, and the noise level ■ is sent out as the AE output. .

Note that the characteristics indicated by ■ and ■ are that if the CSS operation is the first time, the current supplied to the motor 5 stops in the same CSS region, the rotational speed of the motor 5 decreases, and the magnetic The same applies when the head 3 contacts the discs 17 and 18 again, and in this case, when the rotation speed decreases below a, the AE
After the output increases sequentially, it decreases to zero as the rotational speed decreases.

When the CSS operation is repeated in the same CSS region, the convex portions of the protective film in the CSS region are gradually worn away and smoothed. Therefore, the rotational speed b at which the noise level shown in (2) is obtained is lowered, and as shown in (2), the vibration is also reduced and the output characteristic is obtained in which the maximum value of the AE output level is also small.

The relationship between this number of rotations b and the magnetic head 3 being attracted to the CSS area can be obtained through experiments, etc., so when the AE output is monitored and this number of rotations b is detected,
By shifting the CSS area by the slider width of the magnetic head 3, it is possible to prevent the magnetic head 3 from being attracted.

The discrimination circuit 21 sends an enable signal to the memory 22 when the rotational speed of the motor 5 is above a predetermined value and the digital value sent out by the A/D conversion circuit 20 becomes equal to the noise level shown in FIG. Then, the number of rotations sent out by the motor 5 is stored.

Therefore, the magnetic head 3 and the disk 17 or 18
The rotational speed a corresponding to the timing of the contact or separation of the magnetic head 3 that is the last among the plurality of magnetic heads 3 is stored.

The comparison circuit 23 compares the rotation speed stored in the memory 22 with a preset reference value sent out by the reference value setting circuit 24, that is, the rotation speed b shown in FIG.
When the number of revolutions stored in No. 2 becomes less than the reference value, a coincidence signal is sent to the control circuit 8.

When the control circuit 8 receives the coincidence signal and returns the magnetic head 3 to the CSS area, the control circuit 8 changes the distance from the current position of the magnetic head 3 to the CSS area that was used until then.
The distance is calculated by adding or subtracting an offset amount corresponding to the slider width of the magnetic head 3 and sent to the servo control circuit 9.

Based on the distance given from the control circuit 8, the servo control circuit 9 sends a servo signal to the power amplifier circuit 10 for moving the power amplifier circuit 10 by a distance adjusted by an offset amount. Since the power amplifier circuit 10 supplies a current corresponding to this servo signal to the motor 11, the motor 11 is connected to the carriage 12.
is stopped in a new CSS area moved by the slider width.

That is, for example, when the distance from which the offset amount has been subtracted is specified, the vehicle is stopped in a new CSS area moved from the inner circumferential side to the outer circumferential side of the disks 17 and 18, and the offset amount is added. Disk 1
It is stopped in the new CSS area moved from the outer circumferential side to the inner circumferential side of 7 and 18.

The control circuit 8 stores the number of times the matching signal is received, and each time it receives the matching signal, it increases or decreases the offset amount in accordance with the number of times the matching signal is received, and calculates the distance from the initially set CSS area. and instructs the servo control circuit 9.

Therefore, each time the comparator circuit 23 sends out a coincidence signal, the magnetic head 3 shifts from the area on the disks 17 and 18, which had been the CSS area, to the outer or inner periphery by the width of the slider. Perform CSS operations in the new CSS area.

The control circuit 8 controls the floating magnetic head 3 to zero.
When positioning the magnetic head 3 on the cylinder, the distance to the 0 cylinder is calculated by adding or subtracting an offset amount corresponding to the number of matching signals received so far, and the servo control circuit 9 is instructed to move the magnetic head 3.

Then, when returning the magnetic head 3 to the CSS area, the current position of the magnetic head 3 is adjusted by an offset amount corresponding to the number of coincidence signals received so far.
Calculate distance.

[0037]

As explained above, since the present invention does not use the same CSS area of a disk medium continuously, the protective film, which is thinned and has reduced durability, is damaged and the lifespan of the disk medium is shortened. In addition, it is possible to prevent the slider of the magnetic head from being attracted to the smoothed CSS area.

[Brief explanation of drawings]

[Figure 1] Block diagram explaining the principle of the present invention

[Figure 2
] Block diagram of a circuit showing one embodiment of the present invention

[Figure 3
] Diagram explaining the relationship between AE output and rotation speed

[Explanation of symbols]

1 Servo means 2 Detection means 3 Magnetic head 4 Disc media 5, 11 Motor 6 Memory means 7. Comparison means 8 Control circuit 9 Servo control circuit 10 Power amplifier circuit 12 Carriage 13-16 AE element 17, 18 Disc 19 Motor drive circuit 20 A/D conversion circuit 21 Discrimination circuit 22 Memory 23 Comparison circuit 24 Standard value setting circuit

Claims (2)

[Claims] [Claim 1] In a magnetic disk device that performs contact start/stop operation, a magnetic head (3)
a detection means (2) for detecting contact or separation between the disk medium (4) and the magnetic head (3);
) and the disk medium (4), each time a contact or separation between the disk medium (4) and the disk medium (4) is detected, a storage means (6) stores the rotation speed of the disk medium (4), and the rotation speed stored in the storage means (6) is determined in advance. a comparison means (7) that sends out a coincidence signal when the number of revolutions is below a set; and when the comparison means (7) sends out a coincidence signal, the magnetic head (3) moves the magnetic head (3) to the disk medium (4); servo means (1) for shifting the area in contact with the disk is provided, and by repeating the contact start/stop operation, each time the comparison means (7) sends out a coincidence signal, the magnetic head (3) moves toward the disk. A magnetic disk device characterized by shifting the area in contact with the medium 4. 2. In the above magnetic disk device, when shifting the area where the magnetic head (3) contacts the disk medium (4), the area where the magnetic head (3) contacts the disk medium (4) is shifted from the inner circumferential side of the disk medium (4) to the outer circumferential side, or from the outer circumferential side of the disk medium (4). 2. The magnetic disk drive according to claim 1, wherein the slider is sequentially moved toward the inner circumferential side by the width of the slider.