JPH1091930A - Magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the resolution of positional error signals and to conduct the positional control of a magnetic head with high precision by setting each reproducing signal of plural burst signals to the level, which is always above a prescribed value, regardless of the position in the disk radial direction of the head. SOLUTION: The width of each burst signal in the disk radial direction is made 1.5 times the track pitch, for example. Therefore, no voltage level of reproduced signals becomes zero and the resolution of positional error signals is made higher. In other words, more than 50% of the magnetic recording part is always traced about each reproduced signal of A, B, C and D burst signals and the adverse effect on the reproduced output by media noise is reduced. Note that the lowest output voltage of the reproduced signals is made higher than V/2 and the adverse effect caused by electric noise is reduced. Thus, the resolution of positional error signals of the magnetic head is increased and the positional control of the head is done in a highly precise manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive for recording or reading information.

[0002]

2. Description of the Related Art A magnetic disk device records or reads information on a plurality of concentric circles by rotating a magnetic disk and using a magnetic head positioned at an arbitrary radial position on the magnetic disk. With the recent improvement in the performance of computers and other information devices, in such magnetic disk devices, the increase in the recording density of the magnetic disk and the increase in the transfer rate for reading by the magnetic head have become increasingly stronger. Is being requested. And
In order to meet such demands for higher density and higher speed, it is necessary to control the position of the magnetic head with higher precision and speed.

[0003] 3.5 inch or 2.5 inch HDD
In such a small magnetic disk device, the position of the magnetic head has been conventionally controlled using servo pattern information discretely written on a part of the recording circle of the disk. FIG. 4 schematically shows the positional relationship of such servo pattern information on a magnetic disk.
In this figure, each track formed concentrically on a magnetic disk is provided with a plurality of sectors, and servo pattern information is written at the head position of each sector. Then, as indicated by the arrow, the magnetic disk rotates in the disk track direction, and the magnetic head moves in the disk radial direction.

FIG. 5 is an explanatory diagram of a data block relating to servo pattern information. FIG. 5B shows the ratio of the data amount between the servo pattern information and the data information, and the ratio between the two is about 1: 5 to 1:10. FIG.
(A) shows data contents constituting the servo pattern information, and includes an address AGC signal, an erase signal, an address signal created by a gray code, and a burst AGC.
Signals, A, B, C, D burst signals, and GAP burst signals.

FIG. 6A shows a recording pattern of A, B, C, and D burst signals on a magnetic disk, where the hatched portions are magnetically recorded portions.
Each burst signal is formed by alternately writing a signal portion of one track pitch width recorded at a constant frequency and a non-signal portion of the same one track pitch width in the radial direction of the disc. The phases in the track direction are reversed between the A and B burst signals and between the C and D burst signals, and the phases in the track direction are shifted by 90 degrees between the A and B burst signals and the C and D burst signals. Has been written.

FIG. 6B shows that the magnetic head 1 corresponds to FIG.
3 schematically shows the voltage level of the head reproduction signal read when the head is at the position shown in FIG. The magnetic read width of the magnetic head 1 is the same as the track pitch. Since the magnetic head 1 traces half of the magnetic recording portions of the A and B burst signals, the voltage level of the reproduced signal read from these portions is V / V. It becomes 2. Further, since the magnetic head 1 does not trace the magnetic recording portion of the C burst signal, but traces all the magnetic recording portions of the D burst signal, the voltage level of the reproduced signal read from these portions is 0, V Becomes

FIG. 7 shows reproduction signals and their deviation signals when the magnetic head 1 reads the A and B burst signals while moving in the disk radial direction during the seek. FIG. 7 shows only the A and B burst signals, but it is only necessary to consider the C and D burst signals whose phases are shifted by 90 degrees from the A and B burst signals. As shown in this figure, each of the reproduction signals for the A and B burst signals has a period of 2 × track pitch, a phase shift of 180 degrees, a mountain-shaped continuous waveform corresponding to the position of the magnetic head 1, and a maximum voltage. Is V volts, minimum voltage is 0
Become a bolt.

Then, an (AB) deviation signal indicating a deviation between the A burst signal and the B burst signal is obtained, and this deviation signal is used as a position error signal. At this time,
From the C and D burst signals, a (CD) deviation signal whose phase is shifted by a half track pitch from the (AB) deviation signal is obtained. (A-B) In the waveform of the deviation signal, since the position error is large near the top of the mountain, the vicinity of the top is actually cut, and only the range of V / 2 to -V / 2 volts is used. ing. For the position control near the cut top, a (CD) deviation signal whose phase is shifted by a half track pitch is used. As a result, all of the A, B, C, and D burst signals are used for feed control and position control of the magnetic head.

[0009]

By the way, in order to increase the recording capacity of the magnetic disk drive, it is necessary to increase the track density. To increase the track density, a servo system capable of performing high-precision position control is constructed. There is a need to. For that purpose, a position error signal having a good resolution and eliminating the influence of electrical noise is required.

However, as described above, only the range of V / 2 to -V / 2 volts is actually used among the A and B burst signals and the (CD) deviation signal.
The magnetic recording portion where the transducer of the magnetic head emits a reproduction signal is half or less, and the head reproduces an unnecessary portion where necessary magnetic recording is not written in more than half. Therefore, the influence of magnetic noise from the magnetic medium on the reproduction signal output is large. Further, since V / 2 and -V / 2 volts are about half of the reproducible voltage, the influence of electric noise coming from a power supply or the like is large.

As described above, the conventional position control using the A, B, C, and D burst signals is originally susceptible to noise, and is particularly suitable for a high recording density of an MR head and the like and is suitable for media noise. In the case of a sensitive head, a position error signal with better resolution is required.

However, among the reproduced signals of the burst signals in FIG. 6B, the voltage level of the reproduced signal relating to the C burst signal is 0, so that the influence of noise on the C burst signal at this time is different from that of the other signals. It is larger than the burst signal. This is true not only for the C burst signal but also for other burst signals depending on the position of the magnetic head. Therefore, in the end, the conventional technology cannot obtain a position error signal with sufficiently high resolution, and cannot improve the accuracy of position control of the magnetic head by a certain degree or more.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a magnetic disk drive capable of sufficiently increasing the resolution of a position error signal and controlling the position of a magnetic head with high accuracy. And

[0014]

As a means for solving the above-mentioned problems, the invention according to the first aspect of the present invention is directed to a method in which a plurality of phases in the track direction are shifted from each other by a predetermined angle and signal widths in a disk radial direction are different from each other. A burst signal is written for each sector of the track on the magnetic disk,
In a magnetic disk drive for controlling a position of a magnetic head in a disk radial direction based on a level deviation between reproduction signals of two predetermined burst signals read by a magnetic head among the plurality of burst signals, Each of the signals is such that, regardless of the position of the magnetic head in the radial direction of the disk, the reproduced signal read by the magnetic head always has a level equal to or higher than a predetermined value.

According to a second aspect of the present invention, in the first aspect of the present invention, each of the burst signals has a signal width in a radial direction of the disk larger than a track pitch of the disk.

According to a third aspect of the present invention, in the first aspect, the magnetic head has a signal reading width larger than a signal width of a burst signal in a disk radial direction. .

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A shows a recording pattern of A, B, C, and D burst signals on a magnetic disk, and a hatched portion indicates a magnetically recorded portion.
Each burst signal is composed of a 1.5-track pitch width signal portion recorded at a constant frequency and a 1.5-track pitch width non-signal portion also written alternately in the disk radial direction. I have. The phases in the track direction are reversed between the A and B burst signals and between the C and D burst signals, and the phases in the track direction are shifted by 90 degrees between the A and B burst signals and the C and D burst signals. Has been written.

FIG. 1B shows that the magnetic head 1 corresponds to FIG.
3 schematically shows the voltage level of the head reproduction signal read when the head is at the position shown in FIG. The magnetic read width of the magnetic head 1 is the same as the track pitch. Since the magnetic head 1 traces 75% of the magnetic recording portion of the A and B burst signals, the voltage level of the reproduced signal read from these portions is ( 3/4) · V. Similarly, since the magnetic head 1 traces 50% of the magnetic recording portion for the C burst signal and traces all the portions for the D burst signal, the voltage level of the reproduced signal read from these portions is V / 2, V.

As described above, in the present embodiment, the width of each burst signal in the radial direction of the disk is set to 1.5 times the track pitch, so that the overlap between the burst signals always occurs in the track direction. Become. Therefore, when the magnetic head 1 relatively moves on the disk in the track direction, the magnetic head 1 always has A, B, C,
Since any one of the recorded portions of the D burst signal is read, none of these reproduced signals has a voltage level of zero. For example, in FIG. 6B, since the voltage level of the reproduced signal related to the C burst signal is zero, the S / N ratio in this portion is low and the portion is easily affected by noise. In the above, the voltage level of the reproduced signal related to the C burst signal is V /
2 and the S / N ratio in this portion is increased, making it less susceptible to noise. Similarly,
The SN ratio of all the burst signals A, B, and D is also increased, and the burst signals are less affected by noise.

That is, since the position error signal is obtained from the deviation between the reproduction signals related to the burst signal, as the reproduction signal increases, the influence of the media noise and the electric noise becomes smaller and the resolution increases. As a result, the resolution of the position error signal is determined by the magnitude of each reproduced signal of the A, B, C, and D burst signals. In the present embodiment, as described above, the width of each burst signal in the disk radial direction is set to 1.5 times the track pitch.
Therefore, the voltage level of any of the reproduced signals does not become zero as in the related art, and the resolution of the position error signal is high. That is, since the magnetic recording portion of 50% or more of each reproduction signal of the A, B, C, and D burst signals is always traced, the influence of media noise on the reproduction output is reduced. Since the voltage is at least as high as V / 2 volts or more, the influence of electric noise is reduced.
Therefore, the positioning accuracy of the magnetic head can be improved, the track density can be increased, and the storage capacity of the magnetic disk can be increased.

FIG. 2 shows a magnetic head 1 according to this embodiment.
Indicates reproduction signals and their deviation signals when A and B burst signals are read while moving in the radial direction of the disk. FIG. 2 shows only the A and B burst signals, but it is sufficient to consider the C and D burst signals having a phase shift of 90 degrees from the A and B burst signals. As shown in this figure, each of the reproduction signals for the A and B burst signals has a period of 2 × track pitch, a phase shift of 180 degrees from each other, and has a rectangular continuous waveform corresponding to the position of the magnetic head 1. The maximum voltage is V volts and the minimum voltage is V / 2 volts.

Then, an (AB) deviation signal indicating the deviation between the A burst signal and the B burst signal is obtained, and this deviation signal is used as a position error signal. At this time,
From the C and D burst signals, a (CD) deviation signal whose phase is shifted by a half track pitch from the (AB) deviation signal is obtained. (A-B) Since the waveform of the deviation signal has a constant value near the maximum value and the minimum value, the position control of this part is shifted by a half track pitch (CD). Will be used.

In this embodiment, the signal width of the burst signal in the radial direction of the disk is 5 times the track pitch of the disk.
Although the case where the signal width is larger by 0% has been described, the value of the signal width can be set to an arbitrary value of zero or more. For example, even if the signal width is 1%, a certain effect can be obtained.

Further, in this embodiment, a burst signal is used as a configuration for ensuring that the reproduced signal read by the magnetic head always has a level higher than a predetermined value regardless of the position of the magnetic head in the disk radial direction. The technique of making the signal width in the radial direction of the disk larger than the track pitch of the disk was adopted, but the same effect was obtained by keeping the signal read width of the magnetic head It can also be obtained by employing a technique of making the track pitch larger than the track pitch. For example, use a wide magnetic head,
This technique uses a large fringe portion to make it easier to read the signal of an adjacent track. The effects obtained by these techniques are remarkable in high-density tracks of about 10 kTPI or more. FIG. 3 is a characteristic diagram in which the SN ratio at the time of reproducing a burst signal is compared between the present invention and the conventional example. As the track density increases and the track width decreases, the SN ratio decreases. It can be seen that the SN ratio is higher than in the conventional example.

[0025]

As described above, according to the present invention, each reproduced signal of a plurality of burst signals always has a level higher than a predetermined value regardless of the position of the magnetic head in the disk radial direction. Therefore, it is possible to provide a magnetic disk drive capable of sufficiently increasing the resolution of the position error signal and controlling the position of the magnetic head with high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing a recording pattern of each burst signal and a voltage level of a head reproduction signal according to each burst signal in an embodiment of the present invention.

FIG. 2 is a waveform chart showing waveforms of a reproduction signal and a deviation signal obtained by the burst signal of FIG.

FIG. 3 is a characteristic diagram comparing the SN ratio at the time of reproducing a burst signal between the present invention and a conventional example.

FIG. 4 is an explanatory view schematically showing a positional relationship of servo pattern information on a magnetic disk.

FIG. 5 is an explanatory diagram of a data block related to servo pattern information.

FIG. 6 is an explanatory diagram schematically showing a recording pattern of each burst signal and a voltage level of a head reproduction signal related to each burst signal in a conventional example.

FIG. 7 is a waveform chart showing waveforms of a reproduction signal and a deviation signal obtained by the burst signal of FIG. 6;

[Explanation of symbols]

 1 magnetic head A, B, C, D burst signal

Claims (3)

[Claims] 1. A plurality of burst signals whose phases in the track direction deviate from each other by a predetermined angle and signal widths different from each other in a disk radial direction are written for each sector of a track of a magnetic disk. A magnetic head that controls the position of the magnetic head in the radial direction of the disk based on a level deviation between respective reproduction signals of two predetermined burst signals read by the magnetic head, wherein each of the plurality of burst signals is A magnetic disk, wherein a reproduced signal read by the magnetic head always has a level equal to or higher than a predetermined value, regardless of the position of the magnetic head in the disk radial direction. 2. The magnetic disk drive according to claim 1, wherein each of the burst signals has a signal width in a radial direction of the disk larger than a track pitch of the disk. 3. The magnetic disk drive according to claim 1, wherein the magnetic head has a signal reading width larger than a signal width of a burst signal in a disk radial direction.