JPS59217223A - Track follow-up servo system of magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent deterioration in positioning precision due to a defect of the servo medium layer of a magnetic double-layered medium by stacking three stages of respective transducers for data recording and reproduction, servo signal reproduction I , and servo signal reproduction II, at the same place, and obtaining a sum signal of pieces of track servo information and positioning the transducer for data recording and reproduction. CONSTITUTION:Data is recorded and reproduced by the transducer 26, and servo information for positioning this transducer is detected by the transducers 28 and 30 dedicated to servo signal reproduction to detect the difference between the sum signals of the frequencies of respective tracks of the servo signals of the transducers 28 and 30 as a position error signal. Nonmagnetic layers 27 and 29 which are 10-100mum thick are interposed among transducers 25, 28 and 30 for data recording reproduction, servo signal reproduction I , and servo signal reproduction II to reduce the influence of the transducer 26 for data recording and reproduction upon the transducer 28 for servo signal reproduction until it can be ignored.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a track following servo system for a magnetic disk device. Currently, the mainstream method for positioning the magnetic head in the magnetic disk device 7 is the servo surface servo method. In this servo surface servo method, since the servo disk and the data disk are placed apart from each other, errors in positioning accuracy occur due to differences in ambient temperature. Also,
In this servo system, the positioning error of the magnetic head increases, especially as the track density increases, making it difficult to increase the track density and, therefore, to realize a high recording density.

Recently, various data surface servo methods have been studied in order to improve head positioning accuracy, and these data surface servo methods include: ■ Sector servo method that uses part of the data surface ■ Method that uses data information itself ■ Magnetic double layer There is a method in which a disk is used, the lower magnetic film is used as a servo information medium, and the information is used.

The servo method (2) divides the track into sectors and partially inserts servo information, but it tends to have the disadvantage that track servo is not possible in areas other than the area where servo information is input. Positioning accuracy is insufficient in terms of density. Furthermore, since the servo method (2) uses the data information itself, it has the disadvantage that a fluctuation in the output envelope of the data information causes a positioning error. Furthermore, the servo method (■) has two layers of magnetic film, the upper layer is used for data information, and the lower layer is used for servo information. Data and servo information are detected simultaneously by one data head and separated. The positioning error is small because it is used. However, in the servo system using this magnetic double layer medium, Mr. 5N-H-Hansen p1
981 Magazine IBHE Trans, onMagne
tics, Vol. 17, No. 6, pp. 2735-2738, and as shown in FIG. 1, data information and servo information are simultaneously processed by the same head on the same tisf surface.

In FIG. 1, this servo system is a head disk system consisting of magnetic double layer disks 1 to 5, six magnetic heads 6 to 11 corresponding to these, and an actuator 12 for driving the magnetic heads. an assembly, a magnetic head selection circuit for selecting one of the magnetic heads, and a reproduction increaser RLJ unit 16 for simultaneously detecting data information and servo information and reading out the data information by the selected magnetic head.
and a filter 19, a blocking filter 17 for reading servo information, and a reproducing amplifier 20, and further including a recording amplifier 21, a high-frequency F wave unit 18, and a servo notch filter 15 for writing recording data. It includes a bias driver 14 that applies a bias through the servo notch filter 15, and in particular, when writing recording data, a recording current is passed to the selected magnetic head,
When recording data on a disk, it is necessary to detect servo information using a blocking filter 17 and a preamplifier 20. For this reason, during recording, the back voltage of the magnetic head is several volts for the data and servo information reproducing system, and in order to remove this effect, a 1-bias dry no.-14, a notch filter 15, and a high-frequency F wave 518 are added. ing. However, even if these are added, the S/N of servo information during recording deteriorates and the circuit configuration becomes complicated.

Various proposals have been made to improve these problems. Among these proposals, a data recording/reproducing transducer and a servo transducer are placed overlappingly at the same location on one slider of a magnetic head placed on each surface of a magnetic disk, and the servo transducer is There is a method in which servo information of the magnetic double layer medium is obtained by duplication, and track following servo of a data recording/reproducing transducer is performed using the servo information. In this method, the data and servo transducers are separated, so the recording circuit is simple, and the servo information is S/D during recording.
N is improved, the cost of the recording circuit is also reduced, and the positioning accuracy of the magnetic head is increased.

In the comparative examples described above, the magnetic double layer medium must have few defects, and if there are defects, the positioning accuracy of the magnetic head deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to improve this problem and provide a track following T-BO system for a magnetic disk device that reduces deterioration in positioning accuracy due to defects in the servo medium layer of a magnetic double layer medium. In the trunk following servo system of the magnetic disk drive according to the present invention, one data recording/reproducing transducer and two servo transducers are installed at the same location on one slider of a magnetic head arranged on each side of the magnetic disk. - The servo transducers are arranged in three stages, and the sum signal of the signal amplitudes of the two servo transducers is used.
This method performs track-following servo for a transducer for data recording and reproduction.

Hereinafter, the characteristics of the magnetic memory according to the present invention will be explained using comparative examples and examples.

Comparative Example FIGS. 2 and 3 show configuration diagrams of a track following servo system as a comparative example. Figures 2 and 3 (a),
In (b), in the head-disk assembly of the magnetic double layer disks 1 to 5 and the magnetic heads 6 to 11, for example, a data recording/reproducing transformer superimposed on the same part of the slider 24 supported by the magnetic helad arm 8 is shown. Deuser 26 and servo transducer 28
This is a method for positioning the head and recording and reproducing data.

As shown in FIG. 3b, each slider of each head has two transducers.

In the figure, the transducer 2 records and reproduces data.
G, and servo information for positioning this trans dup is detected by a transducer 28 dedicated to reproducing servo signals.Transducer 26 for data recording and reproducing and transducer 28 exclusively for reproducing servo signals.
A non-magnetic (for example, Al2O) layer 27 of 30p is provided between
The servo 4 is inserted by the transducer 26 for data recording and reproduction during recording.
．． The influence on the transducer 28 dedicated to signal reproduction can be reduced or ignored. In addition, with such a two-tiered structure, the deterioration in positioning accuracy due to the difference in thermal density between the disk and the head can be ignored, so the accuracy can be adjusted to within ±0.
Head positioning accuracy of 1 μm or less can be achieved.

Furthermore, due to this two-tiered structure, the servo signal reproducing transducer 28 does not require strict alignment during manufacture. Transducers 26 and 28 are slightly smaller (~50 μm)
) Adequate head positioning accuracy (±0.1 μm) even if misaligned
I can guarantee that. Therefore, it has the advantage of being easy to manufacture.

With this method, the data information recording/reproducing circuit is separated from the T-BO information reproducing circuit, making it very simple.
Moreover, since servo information is not affected by the back voltage during recording, the 8/N ratio is improved, the data information recording/reproducing circuit is similarly simple, and the positioning accuracy and heat difference between the disk and head are negligible. This has the advantage that deterioration caused by

The flow of data and servo information in the comparative example will be explained as follows. In the case of the inner track of the disk, the recording data is inputted to the recording amplifier a21 and then sent to the head selection circuit 13.
The output current of the recording amplifier 21 is caused to flow through the data recording/reproducing transducer v26 of the slider 24 selected by , and data information is recorded on the upper surface of the magnetic disk 3.

Servo information at the time of data recording is taken out by the servo reproduction dedicated transducer 28 on the same slider selected by the head selection circuit 13. That is, since the output of this transducer contains not the servo information on the upper surface of the magnetic disk 3 but the data information and the output due to the leakage magnetic field from the recording and reproducing transducer 26, the reproducing amplifier 22 and low pass filter 23
Only servo information is extracted from 1C and that signal is used as a servo signal.

In the case of the outer tracks of the disk, a data recording/reproducing transducer and a servo signal reproducing transducer which are stacked in two stages on the outer slider are similarly used.

Furthermore, servo information during playback is detected in the same manner as above, and data information is transferred from the top surface of the disk 3 to the magnetic layer on the RAD slider 2.
4 or the data transformer (26) of the magnetic helad core 25 is regenerated and detected by the regenerative amplifier 16 and bypass filter 19.

The same processing method is applied to the other magnetic double layer disk surfaces. This method eliminates the influence of pack voltage during recording, improves the S/N of the servo signal, simplifies the recording circuit, and prevents deterioration of positioning accuracy due to differences in heatstroke. This has the advantage that the degree of head positioning M can be improved as a result.

However, if there is a defect in the servo medium layer of the magnetic double layer medium, the head positioning accuracy deteriorates. If an attempt is made to reduce the allowable number of media defects in the magnetic layer for servo in order to achieve this goal, the disadvantage is that the yield of magnetic double layer disks will be poor and the manufacturing cost will be high.

Embodiment FIGS. 4 and 5 are block diagrams of a track following servo system according to the present invention. Referring to Figures 4 and 5,
Head/disk assembly 'J - consisting of magnetic double layer disks 1 to 5 and magnetic heads 6 to 11.
For example, when the slider 24 supported by the magnetic helad arm 8 is selected for head positioning and data recording/reproduction, the data recording/reproducing transducer 26 and the servo transducer 128 are superimposed at the same location. Servo transducer...from 30 and K,
Performs head positioning and data recording/reproduction.

As shown in Figure 4b), each slider of each head has a structure with three transducers, and servo information is stored in the lower magnetic layer of the magnetic double layer disk at a frequency f. , and f2 are written alternately to each track. Then, the data is recorded and played back using TransDeep 26.
The servo information for positioning this transducer is detected by the transducers 28 and 30 dedicated to servo signal reproduction, and the transducers 28 and 3
The frequency of each track of the servo signal of 0 (fl.

ft) sum signal f1 wave of transducer 28 and f of transducer 30, sum of distribution = A signal, f2 wave of transducer 28 and f2 of transducer 30
The difference A-B (sum of wave components=B signal) is detected as a position error signal (servo signal).

Transducer 26 for data recording and reproduction, transducer 28 for servo signals, and transducer 28 for servo signals.
A non-magnetic material (for example, 8i0□
, resist, etc.) layers 27 and 29 are 10 μm to 100 μm.
The transducer 26 is inserted with a thickness of m to reduce or make it negligible the influence of the data recording/reproducing transducer 26 on the servo signal reproducing transducer 28 during recording.

Also, due to the physical fishing Mio~100 μm between the servo transducer 72B and the servo transducer I [30], defects occurring in the lower servo film of the magnetic double layer medium can be
If the distance is less than the distance between servo transducer 1 and H,
Since one of the two servo signals is detected as a normal signal, the λ1 signal only drops to a maximum of 50%, and the head positioning accuracy is the same as when there is only one servo transducer in the comparative example. Compared to this, deterioration in head positioning accuracy near the location of the defect can be significantly reduced.

The flow of data and servo information in this embodiment is as follows. In the case of the inner track of the disk, the recording data is input to the recording amplifier a21, and the output current of the recording amplifier 21 is selected by the head selection circuit 13. The data is sent to the data recording/reproducing transducer 26 of the slider 24 to record data information on the upper surface of the magnetic disk 3. The servo information at the time of data recording is recorded on the same track of the magnetic disk 3 by the servo sensor) 57 The signal is detected at a position separated by the thickness of the non-magnetic layer 29 (10-100 μm) and converted into a servo signal for the following processing. That is, each servo transducer 1.11 detects data information and servo information in a mixed state at the same time, and extracts only the servo information from the output using a regenerative amplifier 31.33 and low-pass filters 32, 34. , the servo information is divided by the thickness of the non-magnetic layer 29 (10 to 100 μm
) is servo information at a distant position, and the respective information is used to calculate fl and f2, which are the fundamental frequencies of servo information, using 35 (low-pass filter), 36 (bypass filter), 37 (low-pass filter), and 38 (bypass filter). It is separated into components, and its amplitude level is further divided into integrators (3
9, 40, 41, 42) K is detected, and then the sum of f, components (input signal) and the sum of f2 components (B signal) are added to adder circuits 43 and 44 from the same frequency components of the respective integrator outputs.
and k, and the difference between the sum signals A and B is calculated by the differential amplifier 45.
The differential amplifier output signal (A-B) is obtained as a servo signal. In the case of tracks outside the disk, head positioning is performed by similarly using the magnetic head 25 and performing signal processing similar to that described above.

By adopting such a method, it is possible to significantly improve the deterioration in head positioning accuracy due to defects in the servo medium layer of the magnetic double layer medium.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a track following servo system showing an embodiment of the present invention. 1.2, 3, 4.5 Magnetic double layer disk 6.7, 8,
9, 10. 11 Magnetic head 12 Actuator 13 Magnetic head selection circuit 14 Bias driver 15 Servo notch filter 16 Reproduction amplifier 17 Blocking filter 18 Bypass filter 19 Filter 20 Reproduction amplifier 21 Recording amplifier 1 and 2□ U,,@4 23 Low pass filter 24 Magnetic head slider 25 Magnetic head slider 28 Servo transducer I 26 Data transducer 27 Non-magnetic layer 28 Data/pubo combined reproduction transducer 29
Non-magnetic layer 30 Transducer for servo ■ 31 Regenerative amplifier for servo 32 Low-pass filter 33 Regenerative amplifier for servo 34 Low-pass filter 35 Low-pass filter 36 Bypass filter 37 Low-pass filter 38 Bypass filter 39. 40, 41, 42 Separator 43. 44 Adder 45 Operational amplifier

Claims (1)

[Claims] In the track-following servo system (buried servo system) of a magnetic disk device having a magnetic double-layer disk, a magnetic head slider arranged on each magnetic disk has a transducer for data recording/reproduction and a transducer for servo signal reproduction at the same location. -yl and a servo signal reproducing transducer ■ are provided in a three-stage stacked structure, and the magnetic head 2's servo signal reproducing transducer ■ and servo signal reproducing transducer... A track following system for a magnetic disk device, characterized in that a sum signal of servo information is obtained to position a transducer for data recording and reproduction.