JPS63317993A - Magnetic disk - Google Patents

Abstract

PURPOSE:To prevent head crash simply by decreasing or increasing the speed instruction when the deceleration during seek is applied to a track area having a low or high floating quantity setting value respectively. CONSTITUTION:A magnetic disk 2 is supported by a spindle 1 and a magnetic head 4 is positioned on a track of the magnetic disk 2. Then the seek of the magnetic head is applied by controlling a torque of a voice coil motor 3 in response to the speed instruction set so that the average seek time satisfies a prescribed value. In this case, in order to reduce the floating fluctuation during the seek, the speed instruction is set smaller thereby reducing the torque of the voice coil motor 3. In retarding the seek speed, the floating fluctuation at the deceleration is reduced and the minimum floating quantity is 0.2mum or over and the danger of collision with a projection is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk device, and particularly to a magnetic disk device suitable for preventing file destruction due to collision between a magnetic head and a magnetic disk.

[Conventional technology]

Generally, high-density recording has been achieved in magnetic disk drives by reducing the flying height of the magnetic head. However, lowering the flying height also increases the risk of file destruction due to a collision between the magnetic head and the magnetic disk, which is called a head crash.

When reducing the flying height, measures to prevent head crashes have also been taken. Traditionally, measures to prevent head crashes include improving the wear resistance of magnetic heads and magnetic disks, reducing magnetic head vibration by improving actuators and airflow, or smoothing and reducing vibration on the magnetic disk surface.
The main purpose was to remove dust inside the equipment. However, as high-density recording has progressed, it has become difficult to prevent head crashes and reduce the flying height by using these preventive measures alone. One of the reasons for this is that the flying height and flying height fluctuation of the magnetic head vary depending on the seek speed and track position, so head crashes are more likely to occur at specific track positions where the flying height is minimum. To solve this problem, for example, Japanese Patent Application Laid-Open No. 1986-1980 (1983) proposed a method of floating the head slider by using negative pressure.
-113373, and Japanese Patent Laid-Open No. 60-223087, which sets the angle between the head slider and the tangential direction of the disk to increase as the head moves toward the outer circumference, thereby reducing the amount of change in flying height due to circumferential speed. It has been known. In addition to these mechanical means, Japanese Patent Laid-Open No. 61-57085 is also known in which a center track is provided to keep the magnetic head constantly floating near a yaw angle of 0 degrees, and the seek operation is controlled based on this center track.

[Problem that the invention seeks to solve]

Among the above-mentioned conventional techniques, those using mechanical means have a problem in that the apparatus becomes complicated, leading to an increase in cost. Furthermore, the method disclosed in Japanese Patent Application Laid-Open No. 61-57085 controls the track base point during a seek operation as the track with the largest flying height, so there is a problem that random access is no longer possible and the information processing ability of the device is reduced. Ta.

An object of the present invention is to provide a magnetic disk device that controls seek operations and prevents head crashes without reducing the information processing capacity of the device.

[Means for solving problems]

In order to achieve the above object, the present invention reduces the speed command when deceleration during a seek operation is performed in a track area where the flotation height setting value is low; To provide a magnetic disk device that performs seek operation control such as increasing a speed command when performed in a high track area. 2 [Operation] In a magnetic disk device, the flying height of the magnetic head differs depending on the track position. That is, the linear actuator is
Since the angle (yaw angle) between the magnetic head and track on the magnetic disk is constant, the flying height is large on the outer circumference side where the circumferential speed is high and the flying height is small on the inner circumference side where the circumferential speed is low. Become. Further, in a rotary actuator, the flying height is maximum near the middle circumference where the yaw angle is 0 degrees, and the flying height becomes smaller toward the inner circumference and outer circumference. The amount of fluctuation in flying height also varies depending on the track position, seek speed, etc. The difference in the amount of fluctuation depending on the track position is mainly caused by wind turbulence and vibration of the magnetic disk, and generally speaking, the amount of fluctuation varies more on the outer track than on the inner track.
The large amount of movement and the difference in the amount of variation due to seek speed are mainly due to the difference in excitation force, and the larger the speed, the larger the amount of variation (tends to become).

A collision between the magnetic head and the magnetic disk occurs when the flying height of the magnetic head is smaller than the height of the protrusion on the surface of the magnetic disk. Therefore, if the amount of flying height variation increases during seek in a track area where the flying height is small, the risk of collision between the magnetic head and the magnetic disk increases. On the other hand, while seeking a track area with a large flying height, the risk of collision is small even if the variation in flying height is large.

・ ４ ・ Therefore, when passing through a track area with a small flying height,
By determining the speed command during seek so that fluctuations in the flying height are small and fluctuations are large when passing through a track area with a large flying height, the magnetic head's flying height is always adjusted to the magnetic disk without delaying the average seek time. It can be made higher than the protrusion on the surface.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a magnetic disk drive equipped with a rotary type actuator. In FIG. 1, a magnetic disk 2 is held by a spindle 1, and a magnetic head 4 is positioned on the track of the magnetic disk 2.
Data recording/reproduction is performed. This magnetic head 4 is driven by a voice coil motor 6. That is, the seek operation of the magnetic head 4 is performed by controlling the driving force of the voice coil motor 6 in accordance with a speed command set so that the average seek time satisfies a predetermined value. The floating setting value of the magnetic head 4 on the magnetic disk 2 of the disk device changes depending on the yaw angle of the track position and the circumferential speed, as shown in FIG. As is clear from Figure 2, the maximum flying height is 04 μm near the middle track where the yaw angle is minimum, and 0.04 μm near the innermost track where the yaw angle is maximum and the circumferential speed is minimum.
．． The minimum flying height is approximately 3 μm. Also, the third
The shaded area in the figure shows the amount by which the flying height of the magnetic head 4 changes to become lower than the set value due to vibrations of the magnetic disk 2, wind disturbance, etc. during track following control. It can be seen that the amount of fluctuation increases on the outer track where vibrations and wind turbulence increase.The broken line 5 shows the flying height when the amount of fluctuation is maximum, and this is the minimum flying height during track following control. In a magnetic disk drive with 0 disks, the height of the disk surface protrusion of magnetic disk 2 is set to 02μ.
This indicates that there is no risk of a head crash due to floatation fluctuations during track following control since it is set to less than m. However, when the magnetic head 4 performs a seek operation in which it moves between tracks on the magnetic disk 2 at high speed, the magnetic head 2 is strongly vibrated, so the fluctuation in levitation becomes larger than during track following control, and the set levitation The flying height is 02μ while passing through the inner and outer track areas with small amounts.
m or less, there is a risk of collision with a high protrusion of the magnetic disk 2. The shaded area in FIG. 4 shows the amount of variation taking into consideration the variation in floating height during seek, and the broken line 6 is the minimum flying height when using this magnetic disk device. In order to avoid head crashes, this minimum flying height should be reduced to the maximum protrusion of 0.2 on all tracks.
Figure 5 shows the change in the flying height of the magnetic herad 4 when seeking from track 500 on the middle track to track 1100 on the innermost track. The measured value 7 and the drive current 8 of the voice coil motor 3 are shown. At time tl, the track following control system is switched to the speed control system, and so.

A seek operation is started from track No. 1 to track No. 1100, and during ΔT1 until time t2, a drive current flows through the voice coil motor 3 to accelerate or move the magnetic head 4 at a constant speed. t2 to 110
A current flows for deceleration during 612 until time t3 when the vehicle arrives at track 0. As can be seen from the measured flying height change value 7, the variation in flying height during seek is greatest during deceleration.

Since the deceleration operation is performed in the inner track area where the flotation height setting value is low, the minimum flotation height will be 0 when the flotation fluctuation becomes large.
．． There is a possibility that it will be 2 μm or less.

Therefore, in this embodiment, the speed command is set small and the driving force of the voice coil motor 3 is made small in order to reduce the floatation fluctuation during seek.

FIG. 6 shows the measured flying height change value 9 and the drive current 10 of the voice coil motor 3 when seeking from track 500 to track 1100 by decreasing the speed command. It can be seen that by slowing down the seek speed, fluctuations in levitation during deceleration are reduced, and the minimum flying height is 0.2 μm or more, eliminating the risk of collision with a protrusion. However, simply reducing the speed command and increasing the minimum flying height above a certain value will slow down the average seek time.

There is a risk that the filling capacity will decrease. Therefore, as shown in FIG. 7, the speed command when seeking from track 1100 to track 500 on the inner circumference is made smaller so as not to delay the average seek time.

In this case, since the deceleration operation is performed in a track area with a large flying height, the minimum flying height will be 0.2 μm or more even if the flying height fluctuation becomes large, and there is no risk that the magnetic head 4 will collide with a protrusion on the magnetic disk surface. .

Although the present embodiment has been described above with respect to a magnetic disk device equipped with a rotary type actuator, the present invention is not limited to this, and it goes without saying that the present invention can also be applied to a magnetic disk device equipped with a linear type actuator.

〔Effect of the invention〕

According to the present invention, without reducing information processing ability,
Head clarity can be prevented simply by improving the seek operation control method. Furthermore, since the device does not become complicated, it is possible to realize an inexpensive and highly reliable magnetic disk device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing the configuration of a magnetic disk device according to the present invention, FIGS. 2 to 4 are explanatory diagrams showing changes in the flying height of the magnetic head depending on the track position, and FIGS. 5 to 7
The figures are explanatory diagrams showing changes in the flying height of the magnetic head and changes in the drive current of the linear motor during a seek operation, respectively. 1... Spindle, 2... Magnetic disk, 3...
Voice coil motor, 4...magnetic spatula)", 5.5.
...Magnetic head flying height, 7.9. ...Flying height change during seek operation. 8.10... Change in Whiscoil morph drive current during seek operation.

Claims (1)

[Claims] 1. A magnetic disk device that uses a magnetic head to reproduce servo information recorded on a magnetic disk with multiple tracks, drives a motor through feedback control based on the reproduced signal, and moves the magnetic head between tracks and follows the track. In a track area where the required flying height of the magnetic head can be set lower than other track areas, a speed command for decelerating during a seek operation is set smaller than that during an average seek operation, and the required flying height of the magnetic head is set lower than that of other track areas. A magnetic disk device characterized in that, in a track area where the flying height is set higher than other track areas, seek operation control is performed such that a speed command when decelerating during a seek operation is set larger than during an average seek operation. .