JPH10149524A - Magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic disk device capable of executing a tracking based on the magnetic recording of a track on the data area without using a servo mark on the servo area. SOLUTION: This magnetic disk device is provided with a magnetic head 17 consisting of a recording head 18 and a reproducing head 19 for respectively recording and reproducing the information of the magnetic disk, and the reproducing head 19 is divided into plural reproducing head parts 19a, 19b in the direction of track width of the magnetic disk, and the reproduction signal is generated based on the sum of output signals of at least two reproducing head parts 19a, 19b among each reproducing head part, and also based on the difference in amplitude values of the output signals of at least two reproducing head parts, the positional signal for the track of the head is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnetic disk drive having a magnetic head for recording and reproducing information on and from a magnetic disk.

[0002]

2. Description of the Related Art Conventionally, a hard disk drive, which is one of magnetic disk devices built in or connected to a computer or the like, is configured, for example, as shown in FIG. In the hard disk drive 1, a spindle motor (not shown) is provided on a flat surface of a casing 2 formed of an aluminum alloy or the like, and a double-sided magnetic disk driven to rotate at a constant angular velocity by the spindle motor. 3 are provided. Further, an arm 4 is attached to the housing 2 so as to be swingable around a vertical axis 4a.

[0003] A voice coil 5 is attached to one end of the arm 4, and a load beam 4 is attached to the other end of the arm 4.
A head slider 6 having a magnetic head (not shown) is attached via a line b. Magnets 7 a and 7 b are mounted on the housing 2 so as to hold the voice coil 5. The voice coil motor 7 and the magnets 7a and 7b constitute a voice coil motor 7. The magnetic head is formed on the surface of the head slider 6 by a thin film technique or the like, and includes, for example, a recording head and a reproducing head.

In such a configuration, the voice coil 5
When a current is supplied from the outside to the arm 4, the arm 4 rotates around the vertical axis 4a based on the force generated by the magnetic fields of the magnets 7a and 7b and the current flowing through the voice coil 5. As a result, the head slider 6 attached to the other end of the arm 4 moves substantially in the radial direction of the magnetic disk 3 as shown by an arrow X in FIG. Therefore,
The magnetic head provided on the head slider 6 performs a seek operation on the magnetic disk 3.

When a signal current flows through the recording head, information is magnetically recorded on the magnetic disk 3, and leakage of magnetic flux from the magnetization recorded on the magnetic disk 3 is detected by the reproducing head. The information on the magnetic disk 3 is reproduced. As described above, information is recorded / reproduced with respect to a predetermined track of the magnetic disk 3. Here, as shown in FIG. 11, a data area 3a is provided on almost the entire surface of the magnetic disk 3, and a plurality of servo areas 3b are provided for one circumference of the disk (eight in the case shown).
It is provided in. The servo area 3 b is provided so as to divide a track formed substantially in an annular shape in the data area 3 a and to extend from the center of the magnetic disk 3 in the radial direction.

As shown in FIG. 12, a servo mark 3c and an address code 3d corresponding to each track of the data area 3a are formed in the servo area 3b. Each servo mark 3c is composed of an A mark and a B mark distributed from the track center 3e to the outer peripheral side and the inner peripheral side, respectively. These A mark and B mark are usually
It is formed by burst-like repeated magnetization reversal. Thus, when the magnetic head is off-track from the track center to the outside, the amplitude of the reproduction signal from the A mark increases, and when the magnetic head is off-track from the track center to the inside, the amplitude of the reproduction signal from the B mark increases.
Therefore, based on the signal amplitude difference between both the A mark and the B mark, that is, the head position error signal, it is determined how much the magnetic head is shifted outward or inward with respect to the track center, and tracking of the magnetic head with respect to the track is performed. Is performed.

[0007]

In order to obtain a head position error signal of a magnetic head in the above-described conventional hard disk drive 1, it is necessary to form a servo mark 3c on the magnetic disk 3 in advance. . Therefore, there are the following problems. That is, in order to form the servo marks 3c on the magnetic disk 3 with high precision, it is necessary to perform magnetic recording while accurately positioning each track by using a high-precision magnetic recording device. The time for formation is relatively long. In particular, the higher the density of the magnetic disk 3, the more precise the servo marks 3c need to be formed. Therefore, the time for forming the servo marks 3c becomes longer, which causes a problem in terms of productivity and increases costs. There was a problem that would be. Further, in order to perform high-precision tracking with the increase in the density of the magnetic disk 3, it is necessary to increase the number of servo marks 3c per one round of the disk. However, there is a problem that the size becomes narrow.

In view of the above, it is an object of the present invention to provide a magnetic disk drive capable of performing tracking based on magnetic recording of tracks in a data area without using servo marks in a servo area. And

[0009]

According to the present invention, there is provided a magnetic disk drive provided with a magnetic head comprising a recording head for recording information on a magnetic disk and a reproducing head for reproducing the information. Are divided into a plurality of reproducing heads in the track width direction of the magnetic disk, and a reproducing signal is generated based on a sum of output signals of at least two reproducing heads among the reproducing heads. This is achieved by generating a head position error signal based on the difference between the amplitude values of the output signals of at least two read head units.

According to the above structure, the reproducing head is divided into a plurality of reproducing heads in the track width direction of the magnetic disk to be recorded or reproduced. At least two or more reproducing heads independently read the signal of the track. Thereby, based on the output signals from at least two adjacent reproduction heads facing one track, a reproduction signal can be generated by summing them. Furthermore, since the amplitude value of the output signal increases as the contact area with the track increases, the magnetic head moves the inner or outer track with respect to the track based on the difference between these amplitude values. It is possible to determine which side of the side is shifted. Therefore, by performing the tracking servo of the magnetic head using the difference between the amplitude values of the output signals of the reproducing head unit as the head position error signal, the magnetic head can be correctly positioned with respect to the track. In this case, it is not necessary to previously provide a servo mark on the magnetic disk for detecting the head position of the magnetic head and performing the tracking servo. Therefore, the area of the servo area is reduced, and the surface of the magnetic disk is effectively used as a data area. And higher density can be used.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiments described below are preferred specific examples of the present invention,
Although various technically preferred limitations are given, the scope of the present invention is not limited to these forms unless otherwise specified in the following description.

FIG. 1 shows an example of the configuration of a hard disk drive which is an embodiment of the magnetic disk drive of the present invention. The hard disk drive 10 has a spindle motor (not shown) disposed on a flat surface of a housing 11 formed of an aluminum alloy or the like, and a double-sided magnetic disk that is driven to rotate at a constant angular velocity by the spindle motor. 12 are provided. Further, the housing 11
, An arm 13 is attached to be swingable about a vertical axis 13a. A voice coil 14 is attached to one end of the arm 13, and a head slider 15 having a magnetic head 17 as shown in FIG. 2 is attached to the other end of the arm 13 via a load beam 13 b. Magnets 16 a and 16 b are mounted on the housing 11 so as to sandwich the voice coil 14. Then, the voice coil 14 and the magnets 16a, 16b
Thus, the voice coil motor 16 is configured.
The magnetic head 17 is formed on the surface of the head slider 15 by a thin film technique or the like.

In such a configuration, the voice coil 1
When an electric current is supplied from the outside to the arm 4, the arm 13 causes the vertical axis 13 a to move based on the magnetic field of the magnets 16 a and 16 b and the force generated by the electric current flowing through the voice coil 14.
Rotate around. As a result, the head slider 15 attached to the other end of the arm 13 moves substantially in the radial direction of the magnetic disk 12, as indicated by the arrow X in FIG. Therefore, the magnetic head 17 provided on the head slider 15 performs a seek operation on the magnetic disk 12.

When a signal current flows through the recording head 18, information is magnetically recorded on the magnetic disk 12, and leakage of magnetic flux from the magnetization recorded on the magnetic disk 12 is detected by the reproducing head 19. Thus, the information on the magnetic disk 12 is reproduced. As described above, information is recorded / reproduced with respect to a predetermined track of the magnetic disk 12. The above configuration is the same as that of the conventional hard disk drive 1 shown in FIG. 10, but in the hard disk drive 10 according to this embodiment, the magnetic head 17 provided on the head slider 15 is as shown in FIG. The recording head 18 includes a recording head 18 and a reproducing head 19, and the reproducing head 19
Two reproduction head portions 19a and 19b in the track width direction of
Is divided into In the case shown in the figure, the recording head 18 and the two reproducing heads 19a,
19b are all represented by the same width.

As shown in the upper part of FIG. 4, for example, the magnetic head 17 has tracks T1, T2, T
3 (the track width is the recording head 18 and the reproducing head 1
9A and 19B), the amplitudes of the output signals Sa and Sb from the reproducing heads 19a and 19b are, as shown in the middle part of FIG. 19a and 19b are tracks T1, T2,
It is proportional to the length of contact in the width direction of T3, that is, the contact area, and becomes a triangular waveform having a phase shifted from each other by the head width.

The difference S0 between these output signals (S0 = Sa-
When Sb) is obtained, as shown in the lower part of FIG. 4, the track center of each of the tracks T1, T2, T3 is set to 0, and the center of the magnetic head 17, that is, the read head section 19a, 1
When the boundary of 9b is on the left side of the track center (see the upper part of FIG. 4), the output signal difference S0 is negative, and when it is on the right side of the track center, the output signal difference S0
Becomes positive, and the absolute value of the output signal difference S0 is proportional to the distance from the track center.

Therefore, the output signal difference S0 becomes a head position error signal indicating the position of the magnetic head 17 with respect to the track center of the track.
By performing feedback based on the output signal difference S0 to a control circuit (not shown) for supplying a drive current to the voice coil 14, the magnetic head 17 can be controlled to move toward the track center. Thus, tracking servo of the magnetic head 17 with respect to the magnetic disk 12 can be performed. In this way,
When the tracking of the magnetic head 17 is performed, the recording head 18 is positioned with respect to the track center, so that information can be recorded on the track. Further, the reproducing head 18 outputs the sum (Sa) of the output signals Sa and Sb of the respective reproducing head portions 19a and 19b.
By + Sb), the signal is reproduced over the entire width of the track, so that a reproduced signal with almost no deterioration in the S / N ratio can be obtained.

In the above-described embodiment, the tracking servo is performed using the output signal difference (Sa-Sb) between the output signals Sa and Sb from the reproducing head sections 19a and 19b as a head position error signal. For example, FIG.
The head position error signal may be obtained by using the signal processing circuit shown in FIG. The signal processing circuit 20 includes a read head 19a of the read head 19 of the magnetic head 17;
Reproduction amplifiers 21a and 21b for amplifying output signals Sa and Sb from 19b, amplitude detection circuits 22a and 22b for detecting the amplitudes of amplified signals k × Sa and k × Sb from reproduction amplifiers 21a and 21b, and amplitude detection circuits Subtraction circuit 23 for calculating the difference between the signals from 22a and 22b;
A first addition circuit 24 for calculating the sum of the signals from 2a and 22b, a division circuit 25 for dividing a signal from the subtraction circuit 23 by a signal from the first addition circuit 24, and a reproduction amplifier 21a;
It comprises a second addition circuit 26 for adding the amplified signal from 21b.

According to the signal processing circuit 20 having such a configuration, the signals Sa and S from the respective reproducing heads 19a and 19b are provided.
b is amplified by the reproduction amplifiers 21a and 21b, respectively, and then the amplitude is detected by the amplitude detection circuits 22a and 22b. Then, the amplitude signals Aa and Ab are generated, and the subtraction circuit 23, the addition circuit 24, and the division circuit 25 generate the head position error signal Sh represented by Expression (1).

(Equation 1) In this case, the output signal difference S0 (= Sa−Sb) is standardized as compared with the above-described output signal difference, so that the reproduction output fluctuation due to the wavelength change of the signal recorded on the track is canceled out, and a more accurate head is obtained. A position error signal is obtained. Further, the sum signal k × (Sa + S
b) is calculated, whereby a reproduced signal is obtained.

FIG. 6 shows a specific example of the structure of the reproducing head 19 described above. The reproducing head 30 is a magnetoresistive head, and includes a magnetoresistive film 31 and three electrodes disposed at both ends and at the center so as to divide the magnetoresistive film 31 equally in the horizontal direction. 32, 33,
34, and a bias electrode 35 for generating a bias magnetic field. Reproducing head 30 having such a configuration
According to the above, assuming that no current flows in and out of the electrode 33, the potential difference Va between the electrodes 32 and 33 and the potential difference Vb between the electrodes 33 and 34 become the read head portions 30a and 30b, respectively.
Output signal. In this case, the split head including the reproducing heads 30a and 30b can be easily configured with a simple configuration in which the electrode 33 is added to the middle point of the normal magnetoresistive head.

FIG. 7 shows another specific configuration example of the reproducing head 19 described above. The reproducing head 40 is an induction type head, and includes reproducing cores 41 and 42 made of two magnetic materials and a coil 4 wound around each of the cores 41 and 42.
3 and 44. According to the reproducing head 40 having such a configuration, the magnetic flux due to the magnetization of the track passes through the reproducing cores 41 and 42, and the coil 4
Currents Ia and Ib are generated in the currents Ia and Ib.
b is an output signal of each of the reproducing head units 40a and 40b.

FIG. 8 shows another configuration of the magnetic head 17 described above. The magnetic head 50 includes the recording head 5
1 and a reproducing head 52, and the reproducing head 52 has five reproducing heads 52a, 52b, 52c,
It is divided into 52d and 52e. According to the magnetic head 50 having such a configuration, each of the reproducing heads 52a and 52
b, 52c, 52d, output signals Sa, S from 52e
b, Sc, Sd, Se, among the output signals of the four consecutive reproducing heads, calculate the sum of the two reproducing heads arranged side by side, and calculate the difference signal between two adjacent sets of reproducing heads. I do.

For example, for the reproducing heads 52a to 52d, the difference signal S1 is calculated by equation (2).

(Equation 2) Further, the difference signal S2 is calculated by the equation (3) for the reproducing head units 52b to 52e.

(Equation 3) The difference signals S1 and S2 calculated in this manner are as shown in the middle part of FIG. Therefore, when the difference signal S2 is negative and the signal S3 is generated by inverting the difference signal S1 and outputting the inverted signal, the signal S3 is, as shown in the lower part of FIG. 8, of each track T1, T2, T3. When the track center is set to 0, the center of the magnetic head 50, that is, the boundary between the reproducing heads 52b and 52c is located on the left side of the track center (see the upper part of FIG. 8), and becomes negative, and on the right side of the track center. And the absolute value of the signal S3 is proportional to the distance from the track center.

Therefore, the linearity of the position error signal and the head position within one track pitch completely correspond. In this case as well, the signal S1 is changed to (Sa + Sb +
If the standardization is performed by (Sc + Sd + Se), the influence of the recording amplitude on the reproduction amplitude is canceled out, and a more accurate head position error signal can be obtained. Thus, by positioning the magnetic head 50 in the track width direction such that the signal S1 becomes zero, tracking of the magnetic head 50 with respect to the magnetic disk can be performed. In the case shown in the figure, the sum signal (Sb + Sc) of the output signals of the reproducing head units 52b and 52c of the reproducing head 52 is used as the reproducing signal.

FIG. 9 shows the reproduction heads 52a to 52e.
1 is a specific example of a signal processing circuit for processing an output signal from the ASIC. The signal processing circuit 60 includes the reproducing heads 52a, 52b, 52 of the reproducing head 52 of the magnetic head 50.
c, output signals Sa, Sb, Sc from 52d, 52e,
Reproduction amplifiers 61a and 61 for amplifying Sd and Se, respectively
b, 61c, 61d, and 61e, and each reproduction amplifier 61a,
Amplified signal k × S from 61b, 61c, 61d, 61e
a, k × Sb amplitude detection circuits 62 a and 62
2b, 62c, 62d, and 62e, and each amplitude detection circuit 62
a, 62b, 62c, 62d, and 62e, which are addition circuits 63a and 6 that calculate the sum of signals of adjacent amplitude detection circuits.
3b, 63c and 63d, a subtraction circuit 64 for calculating a difference between signals from the addition circuits 63a and 63c, and an addition circuit 63
subtraction circuit 65 for calculating the difference between the signals from b and 63d
And an inverter 6 for inverting a signal from the subtraction circuit 64
6, a changeover switch 67 for switching the signal from the subtraction circuit 64 or the inverter 66 to the inverter 66 when the signal from the subtraction circuit 65 is negative;
And an adder circuit 68 for adding the amplified signal from 1c.

According to the signal processing circuit 60 having such a configuration, the signals Sa and S from the respective reproducing heads 52a to 52e are provided.
b, Sc, Sd, Se are the reproduction amplifier 61a,
After being amplified by 61b, 61c, 61d, and 61e,
Amplitude detection circuits 62a, 62b, 62c, 62d, 62e
Is detected. Then, each amplitude signal Aa, A
b, Ac, Ad, and Ae are generated, and the adders 63a, 63
According to 3b, 63c and 63d, (Aa + Ab), (Ab
+ Ac), (Ac + Ad) and (Ad + Ae) are calculated, and the subtraction circuit 64 calculates difference signals A1 and A2 represented by Expressions (4) and (5).

(Equation 4)

(Equation 5)

When the difference signal A2 is positive, the changeover switch 67 is connected to the subtraction circuit 64, so that the difference signal A1 is output as it is as a head position error signal, and when the difference signal A2 is negative. When the changeover switch 67 is connected to the inverter 66 side, the inverted difference signal, that is, -A1, is output as the head position error signal. Further, the sum signal k × (Sb + Sc) is calculated by the adder circuit 68, whereby a reproduced signal is obtained.

As described above, according to each embodiment, based on the output signals from at least two adjacent read heads facing one track, the difference between the amplitude values of the output signals of these read heads is determined. By performing tracking servo of the magnetic head by using as a head position signal, the magnetic head can be correctly positioned with respect to the track. In this case, it is not necessary to previously provide a servo mark on the magnetic disk for the head position detection of the magnetic head and the tracking servo. Therefore, unlike the conventional method, when manufacturing a magnetic disk, there is no need to perform a servo write step of writing a servo mark while positioning the head one track at a time. Because it's gone
The manufacturing cost of the magnetic disk can be significantly reduced. Further, in the case of a high-density magnetic disk, since no servo mark is required, a reduction in the area of the magnetic disk due to the servo area is eliminated, and the surface of the magnetic disk is effectively used as a data area, so that a higher density is achieved. A high density magnetic disk can be realized.

In the above embodiment, each magnetic head is moved in a substantially radial direction with respect to the magnetic disk by a so-called rotary actuator to perform tracking. However, the present invention is not limited to this. Also, the present invention can be applied to a case where a linear actuator is used. Also, a hard disk device for recording and reproducing data on and from a magnetic disk has been described. However, the present invention is not limited to this, and is applicable to a magnetic disk device using another disk such as a magneto-optical disk as a recording medium.

[0030]

As described above, according to the present invention,
The tracking can be performed based on the magnetic recording of the track in the data area without using the servo mark in the servo area.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing the configuration of an embodiment of a magnetic disk drive according to the present invention.

FIG. 2 is an enlarged perspective view showing a head slider and a magnetic head in the magnetic disk device of FIG. 1;

FIG. 3 is an enlarged bottom view of an example of the magnetic head of FIG. 2;

4 is a graph showing an output signal of each reproducing head unit and a difference signal thereof when the magnetic head of FIG. 3 is moved in a track width direction of a magnetic disk.

FIG. 5 is a block diagram showing a configuration example of a signal processing circuit for processing a signal of each reproducing head unit of the magnetic head of FIG. 3;

FIG. 6 is an enlarged perspective view showing an example of a specific configuration of the reproducing head of FIG. 3;

FIG. 7 is an enlarged perspective view showing another example of the specific configuration of the reproducing head of FIG. 3;

8 is a graph showing an output signal of each reproducing head unit and a difference signal thereof when another example of the magnetic head of FIG. 2 is moved in a track width direction of a magnetic disk.

9 is a block diagram showing a configuration example of a signal processing circuit for processing a signal of each reproducing head unit of the magnetic head of FIG. 8;

FIG. 10 is a schematic perspective view showing a configuration of an example of a conventional magnetic disk drive.

11 is a schematic plan view showing a data area and a servo area of the magnetic disk in the magnetic disk device of FIG.

FIG. 12 is a partially enlarged development view showing a detailed configuration of a servo area in the magnetic disk of FIG. 11;

[Explanation of symbols]

10: magnetic disk drive, 11: housing, 12
..Magnetic disk, 13 arm, 14 voice coil, 15 floating head slider, 16
・ Voice coil motors, 17, 50: magnetic heads
18, 51 ... recording head, 19, 52 ... reproduction head, 19a, 19b, 30a, 30b, 40a, 40
b, 52a, 52b, 52c, 52d, 52e... divided reproduction head unit, 20, 60... signal processing circuit, 21a, 21b, 61a, 61b, 61c, 61
d, 61e: playback amplifier, 22a, 22b, 62
a, 62b, 62c, 62d, 62e: amplitude detection circuit, 23, 64, 65 ... subtraction circuit, 24, 26, 6
3a, 63b, 63c, 63d, 68...
25 ... Division circuit, 30 ... Magnetoresistance effect type reproducing head, 40 ... Inductive type reproducing head, 66 ... Inverter, 67 ... Changeover switch

Claims (5)

[Claims] 1. A magnetic disk drive comprising a magnetic head comprising a recording head for recording information on a magnetic disk and a reproducing head for reproducing information, wherein the reproducing head comprises a plurality of reproducing heads in a track width direction of the magnetic disk. A reproducing unit for generating a reproducing signal based on a sum of output signals of at least two reproducing head units among the reproducing head units, and generating an amplitude value of an output signal of at least two reproducing head units. A magnetic disk drive for generating a head position error signal based on a difference. 2. The magnetic disk drive according to claim 1, wherein the reproducing head is an inductive head including a magnetic core and a coil. 3. The magnetic disk drive according to claim 1, wherein the reproducing head is a magnetoresistive head. 4. The magnetic disk drive according to claim 1, wherein said reproducing head is divided into two reproducing head portions. 5. The magnetic disk drive according to claim 1, wherein the read head is divided into five read head units.