JPH0366078A - Magnetic head positioning system - Google Patents

Abstract

PURPOSE:To improve the positioning accuracy and to attain stable operation by using plural servo magnetic heads and their output signals to position the magnetic heads. CONSTITUTION:Intervals l1, l2,... among plural servo magnetic heads 3a, 3b, 3c,... are selected as an integer multiple of an interval (w) of a servo track, and only when all output signals A, B, C,... of the magnetic heads 3a, 3b, 3c,... has an error, it is discriminated that positioning control of the magnetic heads 3a, 3b, 3c,... has an error. Thus, the positioning without being affected with a local defect of a magnetic disk medium is attained and the unstable positioning control of the magnetic heads 3a, 3b, 3c,... is eliminated.

Description

[Detailed Description of the Invention] [Summary] In a magnetic disk device used as a file device of a computer system, a method for positioning a magnetic head on a predetermined track is affected by local defects in the magnetic disk medium. By establishing a positioning method that does not cause any servo magnetic head output, we aim to realize a highly reliable magnetic disk drive with high and stable positioning accuracy of the magnetic head at low cost. The magnetic head is positioned by a signal, the distance between the magnetic heads is an integral multiple of the servo track distance, and only when there is an error in all the output signals of the magnetic head, the magnetic head is positioned. The configuration is such that it is assumed that there is an error in head positioning control.

[Industrial application field]

The present invention relates to a method for positioning a magnetic head on a predetermined track in a magnetic disk device used as a file device in a computer system.

[Conventional technology]

(1) Overview of magnetic head positioning method Methods for positioning the magnetic head of a magnetic disk drive are broadly classified into servo surface servo methods and data surface servo methods.

The servo surface servo method is a method in which a specific magnetic disk medium among a plurality of magnetic disk media is used as a servo disk, and the position of a magnetic head is controlled based on servo information recorded on the servo disk.

Further, the data surface servo method is a method in which servo information is recorded in a specific sector of a magnetic disk medium, and the position of the magnetic head is intermittently controlled based on the servo information.

In any case, the servo information recorded on the magnetic disk medium is read by a magnetic head, and the positioning of the magnetic head is controlled by the read output signal, and the position of the magnetic head facing the surface of each magnetic disk medium is It's in control.

FIG. 4 is a diagram explaining the conventional magnetic head positioning method, (a) is a block diagram of the servo information reading section, (b)
) is a diagram explaining the relationship between the servo track and the magnetic head,
(c) shows the magnetic head output signal waveform when the magnetic head is correctly positioned, and (d) shows the magnetic head output signal waveform when there is an error in the position of the magnetic head.

That is, as shown in FIG. 2(a), servo information recorded on a magnetic disk medium 1 is read out by a magnetic head 3 provided on a slider 2, amplified by an amplifier 4, and then supplied to a magnetic head positioning servo circuit. There is.

At this time, the servo magnetic head 3 is controlled to be positioned at an intermediate position between adjacent servo tracks 5, as shown in FIG. 2B.

On the other hand, when the servo magnetic head 3 is correctly positioned, the output signal waveform of the magnetic head 3 becomes a triangular waveform of the same size repeatedly, as shown in FIG. 3(c).

On the other hand, if there is an error in the position of the servo magnetic head 3, triangular waveforms of different sizes repeatedly appear, as shown in FIG. 3(d).

In other words, the magnetic head positioning servo circuit performs control so that the waveform shown in FIG. 2(c) is always obtained, thereby positioning the magnetic head.

(2) Conventional defect countermeasures However, if the magnetic disk medium has magnetic defects or scratches from the beginning, or if the magnetic disk medium is scratched or foreign matter adheres to it due to the intrusion of dust etc. while using the magnetic disk drive, If this occurs, an error will occur in the servo information read by the magnetic head 3 at the defective portion, the scratched portion, or the foreign matter adhered portion.

As a result, even though the magnetic head 3 is correctly positioned, the positioning servo circuit operates to eliminate the error, and as a result, the position of the magnetic head 3 becomes unstable.

Conventionally, in order to solve such problems, we have increased the strength of the magnetic disk media against head crashes, improved the flying stability of the magnetic head, and specially selected magnetic disk media used as servo disks to improve error quality. Countermeasures were taken, such as using superior magnetic disk media.

[Problem to be solved by the invention]

On the other hand, the demand for high-density recording on magnetic disk media is increasing, and the demand for stable positioning of the magnetic head is also increasing.

However, there are limits to the quality improvement and selection of magnetic disk media, and manufacturing costs also increase. Further, it is not possible to expect a dramatic improvement in stability.

The technical problem of the present invention is to solve the above-mentioned problems when positioning the magnetic head, and to establish a positioning method that is not affected by local defects in the magnetic disk medium, thereby improving the positioning of the magnetic head. The object of the present invention is to realize a highly accurate, stable, and reliable magnetic disk device at low cost.

[Means to solve the problem]

FIG. 1 is a diagram explaining the basic principle of the present invention.

The present invention is characterized in that positioning is performed using a plurality of servo magnetic heads and their output signals.

That is, a plurality of servo magnetic heads 3a+3bt3c
This is a system in which the i magnetic heads 3a+3b+3ct-... are positioned by output signals A, B, C,... of s..., and the magnetic heads 3a+3b+3c+...
The mutual spacing, t12, . . . is determined by the servo track 5.
The distance W is an integral multiple of the magnetic heads 3a+3b,
3c+... output signals A, B.

It is assumed that there is an error in the positioning control of the magnetic heads 3a13b+3c+... only when there is an error in all of C2....

[Effect]

FIGS. 2(a), (b), and (c) are diagrams for explaining the action. In each figure, ■ indicates the waveform of the output signal A of the magnetic head 3a, ■ indicates the waveform of the output signal B of the magnetic head 3b, ■
is the waveform of the output signal C of the magnetic head 3c, and 2 is the signal waveform used for positioning servo control of the magnetic head.

FIG. 2(a) is a diagram illustrating a case where the servo magnetic head is correctly positioned.

In this case, triangular waveforms of the same magnitude are repeatedly obtained for the output signal A, the output signal B, and the output signal C1, and therefore, this same signal waveform is used for servo control.

FIG. 2(b) is a diagram illustrating a case where a part of the magnetic disk medium has a defect such as a scratch even though the servo magnetic head is correctly positioned.

That is, even though triangular waveforms of the same magnitude are repeatedly obtained for both the output signal A and the output signal C1, the amplitude of the output signal B temporarily decreases.

This is because the servo track traced by the magnetic head 3b has defects such as scratches, whereas the servo tracks traced by the other magnetic heads 3a and 3c have no abnormalities.

In such a case, output signal B is ignored and output signals A and C are used for servo control.

Therefore, the positioning of the magnetic head will not become unstable due to the scratches or the like.

FIG. 2(c) is a diagram illustrating a case where the servo magnetic head is not positioned correctly.

In this case, triangular waveforms of different sizes repeatedly appear in the output signal A, the output signal B1, and the output signal C1. Therefore, this same signal waveform is used for servo control.

As mentioned above, the servo magnetic heads 3a, 3b+3c+
Only when there is an error in all of the output signals A, B, C, ... of the magnetic heads 3a, 3b, 3c+...
By assuming that there is an error in the positioning control of the magnetic heads aa+3b+3c+, etc., the positioning control of the magnetic heads aa+3b+3c+, etc. will not become unstable due to local defects occurring in the magnetic disk medium.

〔Example〕

FIG. 3 is a diagram explaining the embodiment, (a) is a block diagram when servo information obtained from the servo magnetic head is obtained at the same timing, and (b) is a block diagram of the servo information obtained from the servo magnetic head. FIG. 4 is a block diagram of the case where the data are obtained at different timings.

In the same figure (a), a thin film magnetic head 3d is mounted on the slider 2.

3e, the output signals of the magnetic heads 3d and 3e are amplified by amplifiers 4a and 4b and then applied to the logic circuit 6.

The logic circuit 6 performs an AND operation on the error signal of the input servo information signal, and does not accept even if there is a temporary error in one of the input signals.

Therefore, errors in the servo information signal caused by scratches or local defects on the magnetic disk medium l are not used for magnetic head positioning control.

FIG. 4B shows an example of signal processing when there is a relative time difference between the servo information signals obtained by the magnetic healds 3d and 3e from the servo signal units 8a and 8b of the magnetic disk medium 1. .

In the case of FIG. 2B, the magnetic disk medium 1 rotates to the right in the figure. Therefore, the servo information signal obtained from the servo signal section 8a of the magnetic disk medium 1 temporally precedes the servo information signal obtained from the servo signal section 8b.

Therefore, the preceding servo information signal is delayed by the delay circuit 7 by the preceding time and is applied to the logic circuit 6a.

However, in this case, it is necessary to use the servo signal section 8b as the main servo information signal used for magnetic head positioning control so as not to cause a decrease in the response speed of the positioning control by the delay circuit 7.

Further, it is extremely easy to form two thin film magnetic heads on the slider 2 as in this embodiment.

That is, in a thin film magnetic head, one
This is because the same manufacturing process can be used to form one magnetic head or two magnetic heads.

Therefore, there is almost no increase in manufacturing costs due to this. Furthermore, since it is manufactured using photolithography technology, the spacing between the magnetic heads can be manufactured with extremely high precision.

〔Effect of the invention〕

As described above, according to the magnetic head positioning method of the present invention, positioning is performed using a plurality of servo magnetic heads and their output signals.

Therefore, it is possible to perform positioning that is not affected by local defects in the magnetic disk medium, and to realize a highly reliable magnetic disk device with high positioning accuracy and stability of the magnetic head at a low cost. I can do it.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the basic principle of the present invention, and Figure 2 (a
), (b), and (c) are diagrams explaining the action, and in each diagram, ■ is the waveform of the output signal of the magnetic herad 3a,
(2) is the waveform of the output signal B of the magnetic head 3b, (2) is the waveform of the output signal C of the magnetic head 3c, (2) is the signal waveform used for positioning servo control of the magnetic head, and FIG. 3 is a diagram explaining the embodiment. , (a) is a block diagram when the servo information obtained from the servo magnetic head is obtained at the same timing, and (b) is a block diagram when the servo information obtained from the servo magnetic head is obtained at different timing. Figure 4 is a diagram explaining the conventional magnetic head positioning method, (a) is a block diagram of the servo information reading section, (b)
is a diagram explaining the relationship between the servo track and the magnetic head, (
(c) shows the magnetic head output signal waveform when the magnetic head is correctly positioned, and (d) shows the magnetic head output signal waveform when there is an error in the position of the magnetic head. In the figure, ■ is a magnetic disk medium, 2 is a slider, and 3 is a magnetic disk medium.
．． 3a, 3b, 3c, 3d, and 3e are servo magnetic heads, 4.4a+4b is an amplifier, 5 is a servo track, 6 and 6a are logic circuits, 7 is a delay circuit, and 8a and 8b are servo signal sections, respectively. There is. Leaf 1 diagram

Claims (1)

[Claims] A plurality of servo magnetic heads (3a, 3b, 3c, . . .
) is used to position the magnetic heads (3a, 3b, 3c, . . . ) using output signals (A, B, C, . . . ) of the magnetic heads (3a, 3b, 3c, . . . ).・
...) The mutual spacing (l_1, l_2,...) is an integral multiple of the spacing (W) between the servo tracks (5), and the output signals of the magnetic heads (3a, 3b, 3c,...) (A, B, C, . . .) It is determined that there is an error in the positioning control of the magnetic head (3a, 3b, 3c, . . .) only when there is an error in all of the magnetic heads (A, B, C, . . .). Head positioning method.