JPS61974A - Magnetic disc device - Google Patents

Abstract

PURPOSE:To obtain a disc device which has a high storage density even if positional slippage occurs because of the variance of temperature or the like, by conting the number of time of offset for every data and storing the counted value rewriting data on a disc if this counted value of specific data exceeds a prescribed value. CONSTITUTION:Data written on a disc 1 by a head 3 is read out by the same head 3 and is sent to a read error detecting part 11 through a read waveform processing part 10. Data is sent to a computer 12 if read error is not detected (NO), but the total number of errors of this data is conted by an offset number counting part 30 if read error is detected (YES). If this number N is smaller than a prescribed value M, an offset operation circuit 13 performs the operation. If the number N exceeds the value M, data is stored temporarily in a memory 14 and is written on the disc 1 through a rewrite circuit 15 by the head 3. This operation is performed in the steady state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic disk device, and more particularly to an improvement for reducing the rate of data reading errors due to radial positional deviation of a head in a magnetic disk device. It is.

[Background of the invention]

In a magnetic disk drive, in order to obtain the necessary storage capacity, for example, as shown in FIG. 1, disks 1 are stacked with an assembly 2 at regular intervals.

A system is adopted in which the disk 1 is rotated by a spindle 5, and the heads 3 are attached to a carriage 4 in a comb shape so that each surface of the disk 1 has one or more heads 3, and the heads 3 are driven from behind by a linear motor 20.

A positioning reference signal (referred to as servo signal 22) is written on one side of the disk.

A head provided on that surface (this is called a servo head 21) is made to follow and position it.

At that time, even if the servo head 21 is correctly following the servo signal 22, the data head may be affected by the uneven temperature inside the device.
Alternatively, positional deviation may occur due to insufficient mechanical precision such as inclination of the carriage.

The largest positional deviation due to temperature non-uniformity occurs during the time from when the device is turned on until it becomes thermally stable (this is called the rise time). Specifically, if data written immediately after the power is turned on is read out when the device is in a thermally stable state (this is called a steady state), a positional shift will occur. One way to correct this is to slightly offset the head in the radial direction when a data reading error occurs and reread the data.
There is a method of repeating this until no misreadings occur.

This is called an offset operation. An example is described in Japanese Patent Publication No. 46-16349.

Figure 2 shows the operation at that time. Data written on the disk 1 by the head 3 is read by the same head 3 and sent to the read error detection unit 11 via the read waveform processing unit 10. If no read error is detected (N
o), the data is sent to the computing machine 12; If a reading error is detected (YES), a command is issued to the offset operation circuit 13, and after the above-described operation is performed, reading is performed again. However, data written during the rise time may be misaligned each time it is read in a steady state, and the frequency of offset operations may increase. Rise times are typically minutes to tens of minutes, whereas steady state can last a day or more, with an offset each time data written during the rise time is read in steady state. When this operation is performed, the data processing capacity of the disk device is significantly reduced. Therefore, the recording density of the disk device is limited to a value that does not cause an error even if a positional shift occurs. On the other hand, as mentioned above, this rise time is a small amount of the daily operating time, and is a problem only for the data written during that time. This limitation is disadvantageous in increasing the storage capacity of the disk device.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to improve this and provide a disk device that has a high storage density even when positional shifts occur due to temperature changes.

[Summary of the invention]

Therefore, the disk device to which the present invention is applied counts and stores the number of offsets for each piece of data, and when the number of offsets for specific data exceeds a predetermined number, the data is temporarily saved in another memory and then reused again. It is configured so that it can be rewritten onto the disk.

[Embodiments of the invention]

Hereinafter, the present invention will be explained with reference to Examples.

FIG. 3 is a block diagram showing one embodiment of the present invention. If no read error occurs, 3 → 1 → as in the conventional example.
Data is processed in the process of 3→10→11→12. If a read error occurs (YES in the read error detection unit 11)
), the offset number counting unit 30 counts the cumulative number of errors so far for the data. If the number N is smaller than a predetermined value M (for example, five times in this embodiment), the offset operation circuit 13 performs the same operation as in the conventional example. If N is greater than or equal to M, the data is temporarily stored in the memory 14, passes through the write circuit 15 again, and is written to the disk 1 by the head 3. The operation of m: is performed in a steady state.

〔Effect of the invention〕

By performing the above operations, the corresponding data can be read out in a steady state without any positional deviation.

Although the above description has mainly been about deviations due to temperature rise when the power is turned on, the present invention is generally effective when data is written with positional deviations occurring.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a general example of a magnetic disk device, FIG. 2 is a block diagram showing an offset operation, and FIG. 3 is a block diagram illustrating an embodiment of the present invention. In the figure, 1... disk, 3... head, 1o... read waveform processing unit, 11... read error detection unit, 12...
・Computer body, 13... Operation circuit, 14.
...Memory, 15...Writing circuit, 3.0...Offset number counting section. 81 Kokuichi no-"x>Kokuichikogo 49'

Claims (1)

[Claims] 1. means for reading specific data recorded on a magnetic disk with a head; means for detecting whether the data read by the reading means is an error;
means for offsetting the head by a predetermined amount in the radial direction of the magnetic disk when an error is detected by the error detection means, rereading the data, and repeating this until no reading errors occur; and a number of times the offset is performed. A magnetic disk device comprising means for counting the number of times and re-recording the specific data on the magnetic disk when the number of times exceeds a predetermined number.