JPH10172101A - Medium fault detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the probability of a data loss and to improve reliability of a disk device by reducing a floating amount of a head, generating a thermal asperity(TA) and observing it. SOLUTION: Track information and off-track information, etc., of an MR head 2 are detected by a servo data discussion circuit 6. A servo control circuit 10 sends a position control signal to a voice coil motor driver 9 by using these information, and further, controls the position of the MR head 2 by using a voice coil motor. Various parameters of a read/write circuit 3, the servo control circuit 10 and a motor driver 12 are set all by a controlling microprocessor 13. Not only a fault part on a disk, but also a disk projected part are fault sector registered as the TA in the reproducing waveform of the MR head 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for inspecting a recording medium of a disk storage device such as a fixed disk device.

[0002]

2. Description of the Related Art A magnetic thin film such as ferrite or chromium is deposited on a disk surface of a disk storage device by plating or sputtering as a recording medium. The occurrence of defects due to contact scratches with dust and the like is inevitable. Therefore, of course, defective products are eliminated by precise surface inspection etc. with the disk alone,
In general, a method of inspecting a defective portion in the plane after assembling the device and removing the defective portion to perform formatting is generally used.

Conventionally, in a defect inspection after a disk is incorporated in a device, a specific data pattern is given as a write signal to the device under a practical use condition to write the data on the disk surface, and then the data is written through a head of the device. In this case, a defective portion is registered by evaluating a signal read from the defective portion.

[0004] With the increase in recording density, the flying height of the head has been further reduced in order to improve the magnetic recording characteristics, and the amount has been on the order of submicrons. Accordingly, a change in the recording surface state due to contact between the head and the disk surface becomes a problem. In other words, contact between the head and the disk data surface causes defects such as film peeling and contact flaws, and a phenomenon occurs in which data cannot be read.

[0005]

As a matter of course, there is a high possibility that the head comes into contact with the projection of the disk.
In order to improve the reliability of the disk device, it is desirable not to write data on the protrusions of the disk. But,
In the conventional medium defect inspection method, it is not always possible to obtain data including geometric information of a recording surface. for that reason,
In places where reading by contact is likely to be impossible,
I couldn't stop writing data.

[0006]

Recently, a magneto-resistive head using a magneto-resistive effect as a read-only head has been proposed.
(Hereinafter referred to as an MR head). This MR
When the head contacts the magnetic recording surface of the rotating magnetic disk,
Disturbance called thermal asperity (hereinafter referred to as TA) occurs due to temperature rise caused by friction due to contact. Therefore, by reducing the flying height of the head to generate TA and observing it, it is possible to obtain data including not only the magnetic characteristics but also the geometric characteristics of the disk.

On the other hand, the head obtains a levitation force by an air bearing between the head slider and the rotating magnetic disk. Therefore, by changing the rotation speed of the disk,
It is possible to control the head flying height. Therefore, the flying height of the head is reduced by changing the number of revolutions, and if a medium defect inspection is performed using the data obtained at this time, the protrusion of the disk can be removed from the data recording area.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The disk storage device shown in FIG. 1 is a fixed disk device. Usually, one disk device is provided with a plurality of disks 1, and each disk is provided with a write head and a read head.
In the present invention, in particular, the MR head 2 is used as a reproducing head.
Is used. Servo information for detecting the position of the head is written on each surface of the disk 1, and tracks and sectors are uniquely determined based on the servo information. The MR head 2 provided for each disk surface is mounted on a mechanism usually called a carriage 8, and is moved in the radial direction of the disk inward and outward by a voice coil motor 7 as a head moving motor. The spindle motor 11 is driven by a motor driver 12, and its rotation speed is controlled by a microprocessor 13.

The signal read from the MR head 2 is M
The data is sent to a read / write channel 4 connected to the R head 2 and equalized. One of the equalized read signals is sent to the data reproducing circuit 5 and demodulated as read data, and the other is sent to the servo data examination circuit 6. In the servo data examination circuit 6, information such as track information and off-track information of the MR head 2 is detected.
The servo control circuit 10 sends a position control signal to the voice coil motor driver 9 using information such as the track information and the off-track information, and further controls the position of the MR head 2 using the voice coil motor.

Various parameters of the read / write circuit 13, the servo control circuit 10, and the motor driver 12 can all be set by the control microprocessor 13.

FIG. 2 is a flowchart showing one embodiment of a medium defect inspection system using the above-mentioned disk device. Using a dedicated servo track writer, servo track information is written to an inspection disk installed in a disk device in servo track writing 201. Next, in the parameter setting 202, the disk is rotated to reduce the flying speed of the disk for the purpose of reducing the flying height of the head.
Various parameters such as the write circuit, servo control circuit, and motor driver are set. Next, select disk 20
At 3, the disk to be inspected is determined.

Next, in a data write 204, data is written to the inspection disk. The data to be written here may be dibit, tribit,
Various data such as the highest frequency can be considered. In the medium defect check 205, the medium is inspected for defects. Here, if there is a defect on the disk, the defect position is calculated in the defect position calculation 206, and
Record the defect location on the medium. This operation is performed until the recording of the medium defect is completed. After the recording of the medium defect is completed, it is confirmed that the inspection has been executed on all the disks at the all disk inspection end 208. The operation from the parameter setting 202 to the end of all disk inspection 208 is referred to as a medium defect inspection 200. In all the processes, the rotational speed of the disk is reduced in order to reduce the flying height of the head.

After the completion of the medium defect inspection 200, various parameters such as a read / write circuit, a servo control circuit, and a motor driver are set in the parameter setting 209 in order to return the disk rotation speed to the actual use state. Next, in a defective sector calculation 210, a sector in which a defect exists in an actual use state is calculated from data recorded from the defect position record 207. With the defective sector registration 211, a defective sector is registered so that data is not recorded in a sector where a defect exists. After the above steps are completed, the process proceeds to the next inspection.

By the above steps, not only a magnetically defective portion on the disk but also a disk protrusion which is likely to become a defective portion in the future is determined by T
A defective sector is registered as A, and the reliability of the disk device is improved. In the above-described inspection process example, data writing is performed in a state where the flying height of the head is reduced. However, it is needless to say that it is not always necessary to reduce the flying height of the head when writing data. .

The effect of the reduction in the disk rotation speed will be described in more detail.

In FIG. 3, the waveform 31 is the TA in actual use.
FIG. A waveform 32 is a reproduction waveform at the same medium position at the time of low rotation. First, in a reproduced waveform including TA in actual use, T
It is assumed that the influence of A is observed. The dotted line a in the figure is one index, and when the amplitude is smaller than this level, TA
Shall be eliminated. On the other hand, FIG. 3 shows a reproduced waveform when the number of rotations is reduced at the same medium position.
The waveform 32 of FIG. Since there is no change in the thermal diffusion rate, TA
There is no change in recovery speed. Therefore, the area where the influence of TA is observed on the reproduced waveform is from point A to point B. From the point B to the point C, the influence of the TA is eliminated, and in this area, it is possible to perform a more detailed medium inspection at the time of low rotation than at the time of actual use. In other words, by rotating the disk at a low speed, the influence of the TA is reduced, and the medium inspection can be performed in more detail.

In FIG. 4, reference numerals 41 to 43 denote write data at the time of actual use, a magnetization state of the medium by the write data, and a reproduced waveform, respectively, and reference numerals 44 to 46 denote write data at the time of low-speed rotation. Shows the magnetization state of the medium and the reproduced waveform by the write data. It is assumed that the frequency of the write data 41 is the highest frequency limited by the rise of the write current or the like. Using this data, the medium is magnetized as at 42. Arrows in the figure indicate the magnetization direction of the medium. The hatched portion a in the figure is
This indicates a defective portion of the medium, and the defective portion is not magnetized. When the magnetization on the medium is reproduced by the head, a waveform 43 is obtained. FIG. 2B shows a slice level for detecting a defective portion with respect to the reproduced waveform. When the absolute value of the reproduced waveform is equal to or lower than the slice level, it is recognized that there is a defect on the medium. In the case of the waveform 43, since the amplitude of the reproduced waveform is larger than the absolute value of the slice level, a defective portion on the medium cannot be detected. On the other hand, at the low rotation speed, even if the maximum frequency of the write data is the same as that in actual use,
The distance interval at which the magnetization on the medium is reversed becomes shorter, and the medium is magnetized as shown in FIG. Assuming that the same defect (hatched portion a 'in the figure) as that in actual use exists on the medium, the reproduced waveform is 46. When the same slice level c as used in actual use is used, the amplitude of the reproduced waveform becomes smaller than the absolute value of the slice level as shown in the figure, and the defect a 'on the medium is detected. As described above, even when there is an upper limit in the writing frequency, the medium can be inspected more in detail by lowering the speed of the disk than in actual use.

[0018]

According to the above-described process, not only a magnetically defective portion on a disk but also a disk protrusion which is likely to become a defective portion in the future is registered as a defective sector.
The possibility of data loss is reduced, and the reliability of the disk drive is improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a disk storage device (fixed disk device).

FIG. 2 is a flowchart of one embodiment of a medium defect inspection method in the disk device of FIG. 1;

FIG. 3 is a diagram showing a reproduction waveform 31 including a TA in actual use.

FIG. 4 shows write data 41 in actual use, a magnetization state 42 of the medium by the write data 41, and a reproduced waveform 4
3 is a diagram showing write data 44 at the time of low-speed rotation, a magnetization state 45 of a medium by the write data, and a reproduction waveform 46.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disc, 2 ... MR head, 3 ... Read write I
C, 4 ... read / write channel, 5 ... data reproduction circuit,
6: Servo data examination circuit, 7: Voice coil motor,
8 Carriage 9 Voice coil motor driver
10: servo control circuit, 11: spindle motor, 12
... Motor driver, 13 ... Microprocessor, 20
0: medium defect inspection, 201: servo track writing,
202: parameter setting, 203: disk selection, 20
4: Data writing, 205: medium defect confirmation, 206:
Defect position calculation, 207: Defect position recording, 208: All disk inspection completed, 209: Parameter setting, 210: Defective sector calculation, 2110: Defective sector registration, 31: Reproduction waveform including TA in actual use, 32: Same medium Reproduction waveform at low rotation at the position, 41: write data in actual use, 42: magnetization state of the medium by the write data in actual use, 43: reproduction waveform in actual use, 4
4 ... write data at low speed rotation, 45 ... magnetization state of medium by write data at low speed rotation
6. Reproduction waveform at low speed rotation.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 20/18 572 G11B 20/18 572F

Claims (1)

[Claims] A plurality of magnetic disks, a plurality of heads for writing to and reading from the magnetic disk, and a plurality of magnetoresistive heads for reading, parameters can be set so that the disk rotation speed is variable. In a magnetic disk device including a read / write circuit, a servo control circuit, a motor driver, and a microprocessor for operating the circuit and the driver, a medium defect is performed by reducing the flying height of the head compared to actual use. Inspection method.