JPS6052974A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To make a positioning device of a head small-sized and inexpensive by reproducing the servo-information recorded on the surface of a substrate which has a coefficient of thermal expansion equal to that of the substrate of a magnetic disk and does not rotate, by an exclusive servo-head inter-locked with the head. CONSTITUTION:A vertical magnetic recording medium layer 16 on a substrate 12 which consists of the same material as that of a substrate of a disk 1 and does not rotate is magnetized at an interval equal to an interval of a recording track. Its magnetic field distribution is as shown by (b), therefore, when magneto-resistance elements 17, 18 for constituting a servo-head 3 move in the direction of the X axis, a magnetic field intensity in the direction of the Y axis which is detected by the magneto-resistance elements 17, 18 become 17', 18' of (c). Accordingly, voltages observed by electrodes 19, 20 become like 17'', 18'' of (d), and by taking its difference, a servo-signal 21 is obtained. According to such constitution, a magnetized pattern of the servo-surface can be written easily, etc., therefore, the device can be made small-sized and inexpensive.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic disk device in which all recording/reproducing heads can be accurately positioned at recording track positions.

As shown in FIG. 1, the magnetic disk drive has a recording/reproducing head (hereinafter simply referred to as a head) 2 facing each surface of a rotating magnetic disk 1 to record and reproduce information on each surface of the magnetic disk. It is fixed to the actuator 4 by the arm 3 in the shape of a head, and can move together with the actuator in the direction of the straight arrow in FIG. The actuator 4 has the function of moving the head 2 to an arbitrary recording track on the magnetic disk.

Since the magnetic disk 1 and the arm 3 expand and contract depending on the temperature, unless the recording track position is constantly detected and the head position is fully controlled, a deviation will occur between the recording track and the head position. Turn off this misalignment between the recording track and the head.
It's called a truck.

For this reason, one side of the magnetic disk is dedicated to head positioning information (hereinafter referred to as servo information), and this side (
The head corresponding to vc (hereinafter referred to as servo surface) is used as a dedicated head (servo head) for reproducing servo information, and this servo ff[ is used to constantly position the head.

An example of the gutter positioning method using servo information will be explained based on FIG. 2. On the servo surface, drums as shown in FIG. 2 are arranged periodically in the X-axis direction and the Yliltl direction.

The X-axis direction is the radial direction of the magnetic disk, and the y-Rib direction is the circumferential direction, that is, the running direction of the magnetic disk. 6 in the same figure
When the gap force is applied to the servo at the position , the output voltage of the servo head becomes as shown in FIG. 2 6'. Similarly, if the servo head gap is at positions -A and 8, the output voltages will be 7/ and B/, respectively. Playback output 9
If we take the difference in the amplitude of the pulses at the positions 1 and 10, this difference changes as shown in FIG. 11 with respect to the position of the servo head.

75 (If the position coincides with the self-recorded track, then if a certain recording track head is moved all the way, the number of recording tracks crossed can be determined by counting all the zero points of the difference signal.) After moving by the required number of recording tracks, positioning is performed by finely controlling the head so that it is at a position where the front differential signal strength is zero.

The advantage of this method is that servo information is always available and the head position is always recognized. Therefore, by controlling the acceleration/deceleration of the actuator based on the head position and speed, the time required for head movement can be minimized. Can be shortened,
Further, when there is a slight off-track, the head can be positioned on the recording track at high speed and with high precision.

On the other hand, the disadvantage of this method is that one side of the magnetic disk is used as the servo surface and is used exclusively for servo information, and because it records on the entire surface of the button as shown in Fig. 2, the magnetic disk including the servo surface metal is Higher prices and Figure 2 6z7
This is because a circuit to measure the pulse height from a signal such as zBt is required.

Currently, with the spread of personal computers, the demand for compact magnetic disk drives is expanding. Of these, only three sides can be used for data, making it uneconomical. On the other hand, even compact magnetic disk drives are equipped with high-speed, high-precision head positioning mechanisms, and the present invention has been made in view of this current situation.

FIG. 3 is a diagram for fully explaining the present invention.

Reference numeral 12 denotes a substrate having the same coefficient of thermal expansion as the substrate of the magnetic disk 10, and a magnetic material on which servo information is recorded is formed on one side of the substrate. The board 12 detects the servo signal by the servo head 16 and positions the head? It is fixed at an appropriate position 14 to prevent off-track of the recording track and head 2 due to temperature changes when the head 2 is rotated, and does not rotate like a magnetic disk. Servo head °1
Reference numeral 3 denotes an electromagnetic induction head which detects all changes in magnetic flux over time using windings, and detects all servo signals by using an element capable of detecting a direct current magnetic field, such as a magnetoresistive element or a Hall element.

According to the present invention, all sides of the magnetic disk can be used for recording data, and the substrate 12 can be moved along the road in the form of a strip-shaped piece as long as it is large enough to accommodate the locus of movement of the servo head. Unlike the magnetic disk surface, the servo surface has a low relative speed with the head and a much smaller relative movement distance, so it is easy to manage. 1. As will be explained later, writing can be done easily using a simple magnetization button on the servo surface. Therefore, it is possible to make IT smaller and lower in price compared to conventional methods.

Next, the present invention will be explained in more detail based on Examples. Fourth
In figure (to) 12. 1 is a substrate made of the same material as the substrate of the magnetic disk; 15 is a soft magnetic layer; and 16 is a perpendicular magnetic recording medium layer, which are alternately magnetized vertically at intervals equal to the intervals of recording tracks.

17, 1' and 8 are thin films of magnetoresistive elements, both of which are formed on a single substrate, forming a servo head.

Magnetoresistive element IIfX17, 18 is perpendicular magnetic recording layer 1
When the magnetic field produced by 6 is felt in the X-axis direction, the electrical resistance changes depending on the strength of the magnetic field. In particular, the relationship between the magnetic field strength and the change in the electric resistance can be made linear by applying a full magnetic field to an appropriate magnetic field. This causes a voltage change to be observed at the electrodes 19.20 provided at both ends of the magnetoresistive element 17.18.

The magnetic field distribution in the X-axis direction created by the vertical magnetic recording medium 16 on its surface is as shown in FIG. The Y-axis direction magnetic field strengths felt by the elements 17 and 18 are 17' and 1B' of the 41st g1 (two), respectively. Therefore electrode 1
The voltages that can be observed at 9 and 20 are shown in Figure 4) at 17//
, IB11. Now, if we take the difference between the two, we get 21, which is shown in Figure 21 as a servo signal.
is equivalent to

In this example, the recording form on the servo surface is perpendicular magnetization, but if the magnetic path on the servo head side is properly arranged, it can be
It doesn't have to be magnetization.

As described above, according to the present invention, the cost of the servo surface is lower (no space is required, and the circuit for detecting the height of the reproduction output pulse of the servo head is Because the structure of the unnecessary servo head is simple and the price is low, it has excellent features such as high-speed, surface-accurate head positioning that can be achieved at a low cost and in a small space.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a conventional magnetic disk device. Second
The figure is a diagram illustrating an example of a conventional head positioning method. FIG. 3 is a conceptual diagram of the structure of the magnetic disk device of the present invention. Fourth
Figures (7) to (7) are diagrams for explaining the present invention in detail. 1... Magnetic disk 2... Recording/reproducing head 3... Arm 4... Actuator 5... Magnetized button on servo surface 6.7. B... Servo head positions 6', 7', 8
'...The servo head is 6.7. Reproduction output waveform when at position B 9.10...Position 11 where the pulse indicating the head position stands
...Relationship between the height difference of the pulses standing at 9 and 1o, and the servo head position 12...The fixed base on the entire surface of the servo information is 13...The servo head 14...The fixed position of the board 12 15. ...Soft magnetic layer 16...Perpendicular magnetic recording medium layer 17.18...Thin film of magnetoresistive element 19.20...Electrode 17', 1B'...The total amount felt by magnetoresistive element 17.18 71M direction magnetic field 17//, I B11... Voltage 21 appearing at electrode 19.20 More than the difference between 18" and 17" Applicant Suwa Seikosha Co., Ltd. Agent Patent Attorney Tsutomu Mogami 455 Figure 1 4 IQ

Claims (1)

[Claims] In a magnetic disk device having a rotating magnetic disk and a recording/reproducing head that moves between recording tracks on the magnetic disk, a non-rotating substrate gold film having a coefficient of thermal expansion equal to that of the substrate of the magnetic disk; Information (servo information) necessary for positioning the recording/reproducing head is recorded on the surface of the substrate that is not attached to the recording/reproducing head, and the servo information is reproduced by a dedicated servo head that operates in conjunction with the recording/reproducing head. A magnetic disk device characterized in that the recording/reproducing head is positioned.