JPH0495212A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To correct the position errors of the heads with the use of a simple circuit without reducing the data storage capacity of a magnetic disk device by providing two servo heads on both sides of a track distant from a data head in the transverse direction of the track and setting the data head at the center position of the track based on the difference of levels between the data read signals received from both servo heads. CONSTITUTION:A data head 1 is provided to read and write the data to the sectors together with two servo heads 2 and 3 set on both ends of a track distant from the head 1 in the track-width direction. Then the head 1 is set at the center position of the track based on the difference between the data read levels received from both heads 2 and 3. In such a condition, it is just required to equalize the outputs of both heads 2 and 3 to each other without reducing the storage capacity of the data stored in a magnetic disk device. So that no servo information is recorded into each sector. Furthermore such a protective circuit that evades the erasion of the servo information can also be omitted. Thus, the head position errors can be corrected with the use of a simple circuit.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a magnetic disk device that can simplify the circuit configuration without reducing the data storage capacity of the disk. In a magnetic disk device that divides a track formed on a disk into a plurality of sectors and records a gap signal for dividing the sector in each sector, the purpose is to correct the positional deviation of the head. A data head for writing/reading data to/from the sector, and two servo heads arranged offset from the data head on both sides of the track in the width direction, and a data read signal from the servo head is provided. The data head is positioned at the center of the track based on the difference in level.

[Industrial application field]

The present invention relates to a disk device that positions a head using a data surface servo system, and particularly to a magnetic disk device that can simplify the circuit configuration without reducing the data storage capacity of the disk.

In recent years, as magnetic disk drives have been required to be smaller and have larger capacities, there has been a demand for increasing the number of stacked magnetic disks and narrowing the track spacing. For this reason, even if the servo head is positioned on the target track in the servo surface servo method, the data head may deviate from the target track due to the difference in the expansion of the magnetic disk or the arm of the carriage on which the head is attached due to the heat generated by the magnetic disk drive. Problems started to arise.

In order to solve this problem, a data surface servo method has been devised, and an index servo method or a sector servo method has been provided.

In the index servo method, servo information is recorded near an index indicating the head position of a track, and in the sector servo method, servo information is recorded for each sector. Therefore, the sector servo method is generally used because it can obtain more servo information and position the head more precisely, but it does not reduce the data recording area or complicate the circuit configuration. is necessary.

[Conventional technology]

FIG. 4 is a diagram illustrating an example of the prior art.

Figure 4 shows an example of the sector servo system, and Figure 4(a)
is an example of the format of each sector in the sector servo system. Servo information A and B are recorded in the first area of the sector, followed by a gap ■, then an ID of index information for selecting the sector, and then A gap ■ is recorded. Next, a data area in which data is recorded is provided, and then a gap (2) indicating the end of the sector is recorded.

As shown in the figure, servo information A and B are recorded separately from the center of the track, and when the head is positioned at the center of the track, the servo information A and B are read by the head.
The amplitudes of the reproduced waveforms of and B are recorded so that they are equal in magnitude.

Figure 4(b) and (C) are diagrams explaining the relationship between the head position and the waveform read from the servo information.■ in Figure 4(b) is the center of the track, and the range indicated by t is the track. Assuming an interval of , as shown in A and B in FIG. 4(b), servo information A and B are respectively recorded offset by half the track width from the center of the track. When the head is positioned at the center (2) of the track, the amplitudes of the waveforms obtained by reading the servo information A and B are equal in magnitude, as shown in (2) in FIG. 4(C).

In addition, when the head deviates from the track center ■ in the direction of arrow C, as shown in ■ in Figure 4(b), the reproduced waveform of servo information A disappears, as shown in ■ in Figure 4(C). If only the reproduced waveform of servo information B is read out, and the head deviates from the center of the track in the direction indicated by the arrow, as shown in ■ in Fig. 4(b), the head deviates from the center of the track in the direction indicated by the arrow, as shown in ■ in Fig. 4(C). , the reproduced waveform of servo information B disappears and only the reproduced waveform of servo information A is read out.

Therefore, by finding the difference between the amplitude values of the reproduced waveforms of servo information A and B, it is possible to identify how far the head is off the center of the track (■), and the on-track state where the head is positioned at the center of the track (■) can be determined. I can do it.

[Problem to be solved by the invention]

As described above, conventionally, servo information is recorded in each sector, but the area where this servo information is recorded can be used as a data recording area. Therefore, the sector servo method reduces the data storage capacity of the magnetic disk drive.

Furthermore, in order to prevent the servo information recorded in the sector from being erased during data recording, the data writing circuit becomes complicated. Therefore, costs increase.

Therefore, the conventional sector servo method reduces the data storage capacity of the magnetic disk device and is not economical.

In view of these problems, it is an object of the present invention to make it possible to correct head positional deviation in the same way as the conventional sector servo method using a simple circuit without reducing the data storage capacity of a magnetic disk device. It is said that

[Means to solve the problem]

FIG. 1 is a diagram explaining the present invention in detail.

FIG. 1(a) is a side view of the slider 4, and FIG. 1(b) is a side view of the slider 4.
) is a bottom view of the slider 4 facing the disk. 1
, 2.3 are thin film magnetic heads, l is a data head, and 2 and 3 are servo heads.

The slider 4 is made of magnetic heads 1 to 3 using riI film process technology.
It is the basis for creating, and its materials are, for example, An,
O. Then, the lower magnetic layer 5 of the magnetic head 3 is formed on this base, and the gap layer 6 is formed thereon. Then, an insulating layer and a coil layer 7 are formed on the gap layer 6, and then an insulating layer is formed on the coil layer 7, and then an upper magnetic layer 8 is formed thereon.

When the magnetic head 3 is formed, an insulating layer 9 that insulates the magnetic head 2 and the magnetic head 3 is formed, and then the magnetic head 2 is formed on this insulating layer 9 in the same manner as the magnetic head 3. Ru. Then, do the same as above on the magnetic head 2,
A magnetic helad l is formed.

The head core width of the magnetic head 1 is the head core width of the magnetic heads 2 and 3, W, , W3, as shown in WI in FIG. 1(b).
bigger. The head core widths W2 and W of the magnetic heads 2 and 3 are the same.

As shown in the figure, the magnetic heads 2 and 3 are arranged so as to be shifted from the center position of the head core of the magnetic head 1 by the same amount in opposite directions. That is, for example, as shown by the dotted line, if we draw parallel lines ■ and ■ to the head core width of the magnetic head l, one end of the head core of the magnetic head 2 is in contact with the parallel line ■, and one end of the head core of the magnetic head 3 is in contact with the parallel line ■. Parallel line ■
is in contact with

Using the magnetic head 1 configured as described above, FIG.
), perform a format write on the track. The format at this time is divided into gaps (2), IDs, gaps (2), data areas, and gaps (2) as shown in the sectors, and servo information A and B shown in FIG. 4(a) are not recorded.

When a track recorded in this format is read by the magnetic heads 2 and 3, even if no data is recorded in the data area, the magnitude of the magnetization reversal signal read from gaps 1 to 2 is determined by the magnetic head 1. If located at the center of the track, their amplitudes will be equal.

Therefore, the magnetic heads 2 and 3, that is, the servo heads 2 and 3
The positional deviation of the magnetic head 1, that is, the data RAD 1, can be detected from the magnitude of the magnetization reversal signal read. Then, by performing servo control so that the outputs of the magnetic heads 2 and 3 are equal, the magnetic head 1 can be precisely positioned with respect to the target track.

[Effect]

With the above configuration, servo information is not recorded in each sector, so the data storage capacity of the magnetic disk device is not reduced, and it is only necessary to control the outputs of servo heads 2 and 3 to be equal. Therefore, there is no need for a circuit to protect the servo information from being erased, and a simple circuit can correct the positional deviation of the head.

〔Example〕

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention.

Servo information read by the servo head 20 from the servo surface of the magnetic disk is demodulated by the demodulation circuit 19 and sent to the A/D conversion circuit 18 . During coarse control, the processor 10 switches the input of the A/D conversion circuit 18 to the demodulation circuit 19 side, so the A/D conversion circuit 18 converts the analog value servo information into a digital value, and the processor 10
Send to.

The processor 10 uses this servo information to select the servo head 20.
In order to recognize the position of the servo head 20 and position the servo head 20 at the target cylinder, a speed control amount is calculated and sent to the D/A conversion circuit 11. The D/A conversion circuit 11 converts the speed control signal of a digital value into an analog value and outputs the power amplifier circuit 12.
Send to.

The power amplifier circuit 12 supplies current to the voice coil motor 13 in accordance with the magnitude of the applied speed control signal, and the voice coil motor 13 passes through the carriage 14 to the servo head 20 and the magnetic head shown in FIG. 1 to 3, that is, data head 1 and servo heads 2 and 3 are moved to the target cylinder.

When the servo heads 2 and 3 reach the vicinity of the target cylinder, the moving speed of the carriage 14 decreases, so the servo heads 2 read the magnetization reversal signal from the sector shown in FIG. Reproduction waveform comparison circuit 17
The servo head 3 sends out the reproduced waveform to the comparison circuit 17 via the amplifier circuit 16.

FIG. 3 is a diagram illustrating the relationship between the position of the magnetic head and the reproduced waveform.

If the position of the data head 1 is deviated from the center of the track shown in FIG. 1(C) in the direction of the arrow, the position shown in FIG. 3(a)
As shown in the servo head 2 of FIG. 3(a), the amplitude of the reproduced waveform sent out from the amplifier circuit 15 is
The amplitude is larger than the amplitude of the reproduced waveform sent out from the amplifier circuit 16 shown in FIG.

Furthermore, when the data head 1 is positioned at the center of the track shown in FIG. 1(C), the amplitude of the reproduced waveform sent out from the amplifier circuit 15 will change as shown in the servo head 2 of FIG. is equal to the amplitude of the reproduced waveform sent out from the amplifier circuit 16 shown in the servo head 3 of FIG. 3(b).

Furthermore, if the position of the data head 1 is shifted in the direction of arrow C from the center of the track shown in FIG.
As shown in the servo head 2 in FIG. 3C, the amplitude of the reproduced waveform sent out from the amplifier circuit 15 is smaller than the amplitude of the reproduced waveform sent out from the amplifier circuit 16 shown in the servo head 3 in FIG. 3(C).

Comparison circuit 17 sends the above comparison result to A/D conversion circuit 18. When the servo head 20 reaches the vicinity of the target cylinder and shifts from coarse control to fine control, the processor 10 switches the input of the A/D conversion circuit 18 from the demodulation circuit 19 side to the comparison circuit 17 side. A position control signal is sent to the D/A conversion circuit 11, and the voice coil motor 13 is driven in the same manner as described above, so that the carriage 14 is slightly moved so that the difference in amplitude of the reproduced waveforms sent by the controller becomes zero.

〔Effect of the invention〕

As explained above, the present invention enables the data head to be positioned at the center of the track without reducing the data storage capacity of the disk device, and also uses a complex system to prevent the servo information recorded in the sector from being erased. It is possible to provide an economical disk device without the need for a circuit.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the present invention in detail, FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention, FIG. 3 is a diagram explaining the relationship between the position of the magnetic head and the reproduced waveform, and FIG. The figure is a diagram illustrating an example of a conventional technique. In the figure, ■ is the data head, 2, 3.20 is the servo head, and 4 is the servo head.
is a slider, 5 is a lower magnetic layer, 6 is a gap layer, 7 is a coil layer, 8 is an upper magnetic layer, 9 is an insulating layer, 10 is a processor, 11 is a D/A conversion circuit, 12 is a power amplifier circuit, 13 is a A voice coil motor, 14 a carriage, 15 and 16 an amplifier circuit, 17 a comparison circuit, 18 an A/D conversion circuit, and 19 a demodulation circuit. The origin of the present invention is shown in the table below. 1
Sun Moon Su6 Figure Figure

Claims (1)

[Claims] 1) In a magnetic disk device that divides a track formed on a disk into a plurality of sectors and records a gap signal for dividing the sector for each sector, writing data to the sector/ The servo head (1) includes a data head (1) that performs reading, and two servo heads (2) and (3) that are arranged offset from the data head (1) on both sides of the track width direction. 2)
(3) A magnetic disk device characterized in that the data head (1) is positioned at the center of a track based on a difference in level of data read signals from the magnetic disk drive. 2) The above servo heads (2) and (3) are composed of two pieces,
Each head core width is the same and narrower than the head core width of the data head (1), and the head cores are arranged so as to be shifted from each other by the same amount in opposite directions from the center position of the head core of the data head (1). The magnetic disk device according to claim 1. 3) Compare the amplitudes of the magnetization reversal signals read by the servo heads (2) and (3) so that they are at the same level;
3. The magnetic disk device according to claim 1, wherein the magnetic disk device controls the positioning of the data head (1).