Magnetic disk system

• US 5,555,142 A
• Filed: 03/25/1994
• Issued: 09/10/1996
• Est. Priority Date: 09/27/1990
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Imamura, Makoto, Komai, Tomoko, Inoue, Tetsuo, Sakai, Yuji
• Primary Examiner(s): Psitos, Aristotelis
• Assistant Examiner(s): HABERMEHL, JAMES LEE
• Application Number:
  US08/217,867
• Time in Patent Office: 900 Days
• Field of Search: 360/77.06, 360/77.12, 360/113, 360/77.04
• US Class Current: 360/77.06
• CPC Class Codes: G11B 5/3948 the sensitive elements being active read-out elements
• CPC Class Codes: G11B 5/3967 Composite structural arrangements of transducers, e.g. inductive write and magnetoresistive read G11B5/3906 takes precedence
• CPC Class Codes: G11B 5/4886 relative to rotating disc
• CPC Class Codes: G11B 5/59683 for magnetoresistive heads

Abstract

A magnetic disk system comprises a magnetic head for writing data on and reading data from a magnetic disk as a recording medium and a magnetic disk unit having a head positioning mechanism for positioning the magnetic head on a selected track of the magnetic disk without forming servo information on the magnetic disk. The magnetic head comprises an MR film which is disposed parallel to the direction of the width of a track of the magnetic disk, current supplying electrodes disposed to be in contact with both ends of the magnetic film which are opposed in the direction of the track width and a signal detecting electrode disposed between the current supplying electrodes to be in contact with the MR film. The width of the signal detecting electrode is less than 1/3 of that of the current supplying electrodes. The magnetic disk system permits highly accurate alignment of the magnetic head with closely spaced tracks.

Claims

1. A magnetic disk system comprising a magnetic head and a servo control circuit for positioning the magnetic head, in which said magnetic head comprises:

a magnetic film having two ends and a magnetic resistance effect and disposed parallel to a direction of a width of a track of a magnetic recording medium;

a pair of current supplying electrodes in contact with both ends of said magnetic resistance film; and

a signal detecting electrode in contact with said magnetic resistance film and disposed at such an position between said pair of current supplying electrodes that a first reproduced output between said signal detecting electrode and a first one of said pair of current supplying electrodes equals to a second reproduced output between said signal detecting electrode and a second one of said pair of current supplying electrodes when said magnetic film is centered over the track of the magnetic recording medium, and

said servo control circuit comprises;

means for calculating a difference between said first reproduced output and said second reproduced output to produce a position signal of the magnetic head relative to the track; and

means for controlling a position of the magnetic head based on the position signal.

2. A magnetic disk system according to claim 1, in which the position xc of said signal detecting electrode of said magnetic head satisfies:

##EQU2## where Rs(x) is a reproducing sensitivity distribution of the magnetic film and

xc is a relative position of said signal detecting electrode with regard to a physical center (x=0) of the magnetic film, xc having an absolute value greater than 0.

3. A magnetic disk system according to claim 1, in which said signal detecting electrode of said magnetic head has a width narrower than a width of each of said pair of current supplying electrodes.

4. A magnetic disk system according to claim 3, in which the width of said signal detecting electrode of said magnetic head is less than 1/3 of a width of each of said pair of current supplying electrodes.

5. A magnetic disk system according to claim 1, in which said magnetic head further comprises:

an insulating film which is interposed between a first portion of said signal detecting electrode and said magnetic film, and only a second portion of said signal detecting electrode which is adjacent to said recording medium is in contact with said magnetic film.

6. A magnetic disk system comprising a magnetic head and a servo control circuit for positioning the magnetic head, in which said magnetic head comprises:

a magnetic film having two ends and magnetic resistance effect and disposed parallel to a direction of a width of a track of a magnetic recording medium;

a pair of current supplying electrodes in contact with both ends of said magnetic resistance film; and

a signal detecting electrode in contact with said magnetic resistance film disposed between said pair of current supplying electrodes and

said servo control circuit comprises;

means for obtaining a first reproduced output between said signal detecting electrode and a first one of said pair of current supplying electrodes;

means for obtaining a second reproduced output between said signal detecting electrode and a second one of said pair of current supplying electrodes;

means for storing a ratio of the first reproduced output to the second reproduced output when the magnetic head is on-track;

means for calculating a difference between said first reproduced output and said second reproduced output to produce a position signal of the magnetic head;

means for correcting the position signal based on the stored ratio to generate a corrected position signal; and

means for controlling a position of the magnetic head based on the corrected position signal.

7. A magnetic disk system according to claim 6, which further comprises:

a magnetic recording medium having a track having a width wider than a width of the magnetic head; and

means for obtaining the ratio of the first reproduced output to the second reproduced when the magnetic head is positioned at the given track.

8. A magnetic disk system according to claim 6, in which said signal detecting electrode is positioned such that the first reproduced output is equal to the second reproduced output.

9. A magnetic disk system according to claim 8, in which the position xc of said signal detecting electrode of said magnetic head is represented as follows:

##EQU3## where Rs(x) is a reproducing sensitivity distribution of the magnetic film and

xc is a relative position of said signal detecting electrode with regard to a physical center (x=0) of the magnetic film.

10. A magnetic disk system according to claim 6, in which said signal detecting electrode of said magnetic head has a width narrower than a width of each of said pair of current supplying electrodes.

11. A magnetic disk system according to claim 10, in which the width of said signal detecting electrode of said magnetic head is less than 1/3 of a width of each of said pair of current supplying electrodes.

12. A magnetic disk system according to claim 6, in which said magnetic head further comprises:

an insulating film which is interposed between said signal detecting electrode and said magnetic film, and wherein only that part of said signal detecting electrode which is adjacent to said recording medium is in contact with said magnetic film.

13. A method for servo-controlling a magnetic head comprising a magnetic film having two ends and a magnetic resistance effect and disposed parallel to a direction of a width of a track of a magnetic recording medium, a pair of current supplying electrodes in contact with both ends of said magnetic resistance film, and a signal detecting electrode in contact with said magnetic resistance film and disposed between said current supplying electrodes, the method comprising the steps of:

(a) obtaining a first reproduced output between said signal detecting electrode and one of said current supplying electrodes and a second reproduced output between said signal detecting electrode and the other of said current supplying electrodes when the magnetic head is on-track;

(b) obtaining and storing a ratio of the first reproduced output to the second reproduced output when the magnetic head is on-track;

(c) obtaining a first reproduced output between said signal detecting electrode and a first one of said pair of current supplying electrodes and a second reproduced output between said signal detecting electrode and a second one of said current supplying electrodes during reproduction of the magnetic recording medium;

(d) means for calculating a difference between said first reproduced output and said second reproduced output to produce a position signal of the magnetic head;

(e) means for correcting the position signal based on the stored ratio to generate a corrected position signal; and

(f) means for controlling a position of the magnetic head based on the corrected position signal.

14. A method according to claim 13, in which said step (a) comprises a substep of positioning the magnetic head at a given track of the magnetic recording medium having a width wider than a width of the magnetic head.