JPH04109421A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To simultaneously execute a head positioning control and a floating height control by detecting simultaneously head in-surface position information and height information and performing a feedback control using these pieces of information. CONSTITUTION:One pair of sensor means 1 and 2 provided at a head part are disposed at intervals of an odd number multiple of 1, 2 of a track pitch, and a detecting signals to be changed in accordance with a distance from a track are generated respectively. The height information from a disk surface of the head part is detected by a sum signal of detecting signals of this one pair of sensor means 1 and 2, and the position information of the head part to a track in the radial direction is detected by a difference signal out of the detecting signals. Consequently, when information is read and written by positioning the magnetic head provided in the head part to a specified track of such a magnetic disk as of a discrete track system, the position information of head part in the disk surface and the height information can simultaneously be detected. By this method, the head positioning control and the height control are simultaneously performed.

Description

[Detailed Description of the Invention] [Summary] Regarding a magnetic disk device that employs a discrete track method, head positioning control and flying height control are performed by simultaneously detecting head position information and height information within the disk surface. The purpose is to enable simultaneous execution, and for discrete track type magnetic disks that have multiple tracks and grooves separating each track on the surface alternately, it is possible to float above the magnetic disk surface and move in the radial direction. In a magnetic disk device that is equipped with a head unit and that positions the magnetic head provided in the head unit on a specific track to read and write information, the magnetic head is arranged at an interval of an odd multiple of 172 of the track pitch and is adjusted according to the distance from the track. A pair of sensor means for generating a changing detection signal is provided in the head part, and a height detection means for detecting height information of the head part from the disk surface based on a sum signal of the detection signals of the pair of sensor means. , and position detection means for detecting positional information of the head portion in the radial direction with respect to the track based on a difference signal between the detection signals of the pair of sensor means.

[Industrial application field]

The present invention relates to a magnetic disk device that is widely used as an external storage device for computer systems, and particularly to a magnetic disk device that uses a discrete track method.
The present invention relates to a magnetic disk device that is capable of simultaneously detecting position information and height information of a head unit within a disk surface, and using these information to simultaneously perform head positioning control and flying height control. .

In recent years, the capacity of magnetic disk devices has increased significantly, and, for example, the track width has reached the order of 10 μm.

However, increasing the track density beyond this will cause head side crosstalk (stains when writing to the media).
etc., and are difficult to solve using conventional techniques. Therefore, a discrete track system is being considered, which in principle causes almost no side crosstalk.

Another obstacle to increasing i-rack density is
There is an off-track problem. This is a phenomenon in which the data head shifts from the track center due to temperature changes or the like when performing servo positioning on the servo surface, but it can be prevented if position information can be obtained from the data head.

Furthermore, in order to increase the recording density, it is important to make the flying height of the head as low as possible, and if information on the flying height can be obtained, it is possible to control it even lower and stably.

Therefore, in magnetic disk drives that employ the discrete track method, head positioning is achieved by simultaneously detecting the position information of the head section within the disk surface and the height information, and performing feedback control using these signals. It is desired to be able to perform control and flying height control simultaneously.

[Conventional technology]

Conventionally, the discrete track system in magnetic disk devices has been known in principle, but because it is difficult to realize, almost no technology for its concrete implementation is known.

[Problem to be solved by the invention]

When employing a discrete track system in a magnetic disk drive, it is necessary to obtain positional information of the head section within the disk surface and perform accurate positional control using feedback control. Furthermore, at lower flying heights,
It is desirable to obtain a flying height signal at the same time and use this to control the flying height, but there has been a problem in that no concrete implementation means for this has been proposed.

The present invention aims to solve the problems of the prior art, and provides a magnetic disk device that employs a discrete track system, in which in-plane position information of a head,
By making it possible to simultaneously detect height information and performing feedback control using the information detected in this way, it is possible to simultaneously execute head positioning control and flying height control. The purpose is

[Means to solve the problem]

As shown in the principle structure of FIG. 1, the present invention is applied to a discrete track type magnetic disk having a plurality of tracks and grooves separating the tracks alternately on the surface. In a magnetic disk device that is equipped with a head section that is movable in the radial direction and that positions a magnetic head provided on the head section on a specific track to read and write information, a pair of sensor means 1 and 2 are connected to the head section. 1/2 of track pitch
The height detecting means 3 generates detection signals that vary according to the distance to the trunk, and detects the disk in the head section by the sum signal of the detection signals of the pair of sensor means 12. Detects height information from the surface,
This pair of sensor means 1.2 is detected by the position detection means 4.
The position information of the head portion in the radial direction with respect to the track is detected based on the difference signal between the detection signals of the head portion.

Furthermore, the present invention makes it possible to adjust the height of the head section using the vertical actuator 5 in such a magnetic disk device, and also enables the feedback control means 6 to adjust the height of the head section.
The detected height information of the head section is compared with the flying height command signal to detect an error, and the vertical actuator 5 is controlled according to this error, thereby adjusting the flying height of the head section externally. It is designed to follow the flying height command from .

[Operation] A pair of sensor means provided in the head section are arranged at an interval of an odd multiple of 1/2 of the track pitch, and each generates a detection signal that changes depending on the distance from the trunk. The height information of the head section from the disk surface is detected by the sum signal of the detection signals of this pair of sensor means, and the position information of the head section in the radial direction with respect to the track is detected by the difference signal of the detection signals. , when positioning the magnetic head installed in the head unit on a specific track and reading/writing information on a discrete track type magnetic disk, the position information and height information of the head unit within the disk surface are simultaneously detected. Using this information, head positioning control and height control can be performed simultaneously.

At this time, the height of the head part can be adjusted by the vertical actuator, and the detected flying height information of the head part is compared with the flying height command signal by the feedback control means to detect an error. The flying height of the head portion may be made to follow the flying height command from the outside by controlling the vertical actuators according to the error.

[Embodiment] FIG. 2 shows an embodiment of the present invention, and shows a schematic configuration of a flying height and positional deviation measuring section according to the present invention.

In FIG. 2, reference numeral 11 denotes a magnetic disk, on which separated magnetic layers 131, 13□, and 133° forming discrete tracks are formed concentrically on a flat substrate 12. In this case, the track width, that is, the magnetic layer 13. ．． The width of 13□, 13z, - is 1 to 3 μm
That's about it.

A head section (not shown) floats above this magnetic layer to form a magnetic layer 13. ．． 13□1131.・−
Information is written to and read from each magnetic layer 13! , 13□, 133. - and are separated from each other, side crosstalk to adjacent tracks is extremely small.

Reference numerals 14 and 15 indicate sensor electrodes provided on the head portion, and when the magnetic disk 11 rotates, a small gap is created between the sensor electrodes and the magnetic disk surface as the head portion floats.

The sensor electrodes 14, 15 are connected to the track width of the magnetic disk 11, that is, the magnetic layers 13, . 13□, 133. When the width of the sensor electrodes 14 and 15 is approximately equal to the gap width, that is, the spacing between the magnetic layers, the width of the sensor electrodes 14 and 15 is approximately the same as the track width, and the sensor electrodes 14 and 15 are arranged with a slight gap between them.

Or, use a similar pair of sensor electrodes at 1/2 of the track pitch.
They may be arranged at intervals that are an odd multiple of .

As a detection principle for the sensor electrodes 14, 15, a capacitance type or a magnetic sensing type can be used. That is, the sensor electrodes 14,15 produce an output that decreases as the distance from the track increases.

16 and 17 are modulation circuits, each of which connects the sensor electrode 1.
The magnitude of electrostatic capacitance or magnetic induction between 4.15 and the surface of the magnetic disk 11 is converted into an electrical signal and output. 1
8.19 is an operational amplifier, and each modulation circuit 1
6. Output the sum signal and difference signal of the output of step 17. In this case, the sum signal represents the flying height of the sensors 14, 15 from the surface of the magnetic disk 11, and the difference signal represents the positional deviation of the sensor electrodes 14, 15 from the track center.

FIG. 3 explains changes in the sum signal and difference signal depending on the sensor position, and shows the position of the sensor electrodes 14 and 15, the corresponding difference signal (position signal), and the sum signal (flying height).
It shows.

Now, if we take the difference between the detection signal based on the sensor electrode 14 and the detection signal based on the sensor electrode 15, the sensor electrode 15
In the case (1) where the sensor electrode 14 is directly above the magnetic layer 132, for example, the difference signal output is the minimum, and in the case (2) where the sensor electrode 14 is directly above the magnetic layer 132, the difference signal output is the minimum. is maximum, and in the middle thereof, the magnitude of the difference signal changes linearly as shown in the figure, depending on the positional shift. This relationship is
The sensor electrodes 14.15 are connected to the magnetic layer 13. , 13. , 133
．． ... - occurs repeatedly at each position of the magnetic layer by moving over it.

Therefore, depending on the magnitude of this difference signal, the sensor electrode 14
．． 15 positions on the magnetic layer can be detected.

On the other hand, the sum of the detection signals of both sensor electrodes 14.15 is the sum of the detection signals of both sensor electrodes 14.15. ．． 15 is magnetic [13□, 13□133,”
It is clear that even if the sensor electrodes are moved one above the other, if the sizes of both sensor electrodes are determined as described above, they will always remain constant.

Therefore, depending on the magnitude of this sum signal, even in the case of a discrete track type magnetic disk, it is possible to accurately detect the flying height from the magnetic layer surface.

In general, in high-density magnetic disks, the magnetic film thickness is on the order of submicrons, but the flying height of the magnetic head is also less than that. It can be sufficiently detected by grounding. Further, in the case of an iron oxide magnetic layer, since the dielectric constant is high, detection with higher sensitivity is possible.

FIG. 4 shows another example of the structure of a magnetic disk, in which the substrate 12 itself has a grooved structure, and a magnetic layer 13 is uniformly provided thereon.

In the case of a magnetic disk having the structure shown in FIG. 4, by applying the flying height and positional deviation measurement method shown in FIG. 2, the magnetic layer of the sensor electrode can be measured in the same manner as shown in FIG. It is possible to measure the flying height from the ground and the positional deviation from the track.

FIG. 5(a) shows an example of the configuration of the sensor section, and shows an example in which a sensor electrode is provided for a magnetic head slider 21 of a normal air bearing type. , (a) is a side view, and (b) is a bottom view.

The magnetic hent slider 21 has slider rails 23 and 24 on both sides of the air bearing surface 22, and is configured to fly due to the pressure of the air bearing surface based on the airflow accompanying the rotation of the magnetic disk when placed on the magnetic disk surface. has been done.

Shallow grooves 25.degree. 26 are provided on one slider rail 230 surface of the bottom surface of such a magnetic herad slider 21, and sensor electrodes 27, 28 are formed in the grooves by a method such as spackling. Note that 29 is a magnetic head, which is usually provided on the rear end surface of the magnetic head slider 21.

Usually, the electrodes 27 and 28 are made of metal, and their surfaces are softer than the surfaces of the slider rails 23 and are more susceptible to scratches.
Electrodes 26,27 are provided inside the grooves 25,26 and are slightly concave than the surface of the slider rail 230 to provide mechanical protection.

The centers of the sensor electrodes 27, 28 are made to coincide with the center of the magnetic head 29, or are kept a certain distance apart (generally an integral multiple of the track pitch).

In the system using the magnetic hent slider 21 of the air bearing type shown in FIG. 5, the flying height can be kept almost constant by the air bearing, so small-scale flying control is sufficient. In other words, control may be performed such as increasing the flying height slightly at startup, or raising it slightly during seek.

Alternatively, if there is large dust or the like adhering to the disk surface, control is performed to avoid collision with it.

FIGS. 6(a), (b), and (C) show other configuration examples of the sensor section, which do not use air bearings,
This shows the case of a magnetic head unit of the type that operates by performing positioning control and flying height control only by active control, (a) is a front view, (b) is a side view, (
C) is the dorsal gyrus.

In this case, sensor electrodes 33 and 34 are provided on the oblique front surface 32 of the magnetic head unit 31. In this structure, almost no air bearing surface is required, and therefore a compact head can be constructed. In addition, in FIG. 6, 35 is a magnetic head, and the magnetic head 35 is a magnetic head.
It is provided at the lower part of the end surface 36 on the opposite side of 1. The positional relationship between the sensor electrodes 33, 34 and the magnetic head 35 in this case is the same as in the embodiment shown in FIG.

FIG. 7 shows an example of the configuration of a flying height control system, in which signals from two electrodes provided on the head section 41 are added by an adder 42 to create a flying height signal. . This signal is subtracted from the flying height instruction value given from the outside in the matching section 43 to generate an error signal. The obtained error signal undergoes necessary signal processing in the controller 44, is amplified through the power amplifier 45, and is applied to the actuator 46. As a result, the actuator 46 moves the head section 41 up and down, so that the head section 4 is maintained at a predetermined flying height above the surface of the magnetic disk 470. Note that a piezoelectric element can be used as a means for slightly vertically displacing the actuator.

FIG. 8 shows an example of the configuration of the modulator in the circuit of FIG. 2, and shows the case of a capacitance detection method, in which the capacitance C152 of the sensor electrode is inductance,
3 is an oscillation circuit, and 54 is an AM detector.

In FIG. 8, the capacitance C of the sensor electrode changes by a small amount ΔC in accordance with the change in distance from the magnetic disk surface.

The oscillation circuit 53 has an inductance L and a capacitance C+ΔC
The oscillation frequency changes based on a change in the minute capacitance ΔC that accompanies a change in the distance between the sensor electrode and the magnetic disk surface. The output of the oscillation circuit 53 is detected by an AM detector 54 to generate an output.

FIG. 9 explains the change in output in the circuit of FIG. 8.

That is, the relationship between the oscillation frequency f and the amplitude of the oscillation circuit 3 is as shown by a solid line when there is no change in the capacitance of the sensor electrode, but as the minute capacitance ΔC in the sensor electrode changes, it becomes, for example, a broken line. Changes as shown in . Therefore, the output of the AM detector 54 at this time changes from point A to point B, and an output signal indicating a change in the position of the sensor electrode can be obtained.

FIG. 10 shows a specific example of the configuration of the circuit shown in FIG. 8.

In FIG. 10, corresponding to the AM detector 54 in FIG. 8, a rectifier consisting of a diode 55 and a capacitor 56 . A low-pass filter consisting of a resistor 57 is shown, thereby making it possible to obtain an output that detects a minute change in capacitance 51 based on the displacement of the sensor electrode, as shown in FIG.

Note that the position control of the head section on the disk surface using the difference signal between the detection signals of both sensor electrodes can be performed in the same manner as in the prior art.

〔Effect of the invention〕

As described above, according to the present invention, in a magnetic disk drive employing a discrete track system, information on the position of the head within the disk surface and information on the height from the disk surface can be detected simultaneously. Further, by performing feedback control using the head height information detected in this manner, it is possible to control the flying height of the head.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a diagram showing an embodiment of the present invention, Fig. 3 is a diagram illustrating changes in the sum signal and difference signal depending on the sensor position, and Fig. 4 5(a) and 5(b) are diagrams showing an example of the structure of the sensor section, and FIGS. 6(a), 6(b), (
C) is a diagram showing another example of the configuration of the sensor section, FIG. 7 is a diagram showing an example of the configuration of the flying height control system, FIG. 8 is a diagram showing an example of the configuration of the modulator in the circuit of FIG. 9 is a diagram illustrating changes in output in the circuit of FIG. 8, and FIG. 10 is a diagram showing a specific example of the configuration of the circuit of FIG. 8. 1.2 is a pair of sensor means, 3 is flying height detection means, 4
5 is a position detection means, 5 is a vertical actuator, and 6 is a feedback control means. Diagram showing the basic configuration of the present invention

Claims (2)

[Claims] (1) A discrete track type magnetic disk having a plurality of tracks and grooves separating the tracks alternately on its surface is equipped with a head section that floats above the surface of the magnetic disk and is movable in the radial direction. In a magnetic disk device that positions a magnetic head provided in a head unit on a specific track to read and write information, a detection device is arranged at an interval of an odd multiple of 1/2 of the track pitch and changes depending on the distance from the track. A pair of sensor means (1, 2) each generating a signal is provided in the head part, and the height of the head part from the disk surface is determined by a sum signal of the detection signals of the pair of sensor means (1, 2). height detection means (3) for detecting information; and position detection means (4) for detecting radial position information of the head relative to the track based on a difference signal between the detection signals of the pair of sensor means (1, 2). A magnetic disk device characterized by having the following. (2) In the magnetic disk device according to claim 1,
a vertical actuator (5) that adjusts the height of the head section;
), and feedback control means () that compares the detected head height information with a flying height command signal to detect an error, and controls the vertical actuator (5) according to the error.
6) A magnetic disk device characterized in that the flying height of the head section is made to follow the flying height command from the outside.