Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of biasing or erasing
Reexamination Certificate
1998-06-26
2001-07-17
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of biasing or erasing
C360S075000, C360S046000
Reexamination Certificate
active
06262858
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a magnetic disk device which reproduces information from a magnetic disk by using a magneto-resistive head wherein a sense current is supplied to the head and a change of a resistance of the head for the disk in a magnetic field is detected as a read data signal.
Recently, a magnetic disk device using a magneto-resistive (MR) head to reproduce information from a magnetic disk has been made widely available because the MR head provides a high output level of a read data signal when reading data from the magnetic disk. The MR head has a resistance which varies depending on a magnetic field applied to the magnetic disk. In the magnetic disk device, a sense current is supplied to the MR head as a bias current, and a change of a resistance of the MR head for the disk in the magnetic field is detected as a read data signal. In the magnetic disk device, the sense current supplied to the MR head is predetermined.
In a conventional magnetic disk device of the above type, the sense current supplied to the MR head is predetermined so that given reproduction characteristics of the MR head in a high-temperature operating condition are obtained and a useful life of the MR head in conformity with a given useful life of the magnetic disk device is satisfied.
(2) Description of the Related Art
In a conventional magnetic disk device using the MR head, the sense current supplied to the MR head is predetermined or fixed to a constant level so that the MR head provides given reproduction characteristics in a high-temperature operating condition, in order to allow the MR head to satisfy a useful life of the MR head in conformity with a given useful life of the device.
The sense current which is optimum to be supplied to the MR head varies depending on an operating condition of the MR head. Japanese Laid-Open Patent Application No. 8-293165 which is assigned to the applicant of the present invention discloses an automatic calibration method for a magnetic disk device having a plurality of MR heads. In the automatic calibration method of the above publication, a plurality of initialized sense current values with respect to the plurality of MR heads are predetermined according to the operating condition of each of the MR heads. In order to set the sense current at the optimum level, the sense current supplied to each of the MR heads is predetermined to be set to one of the initialized sense current values depending on the operating condition of each of the MR heads.
However, in the conventional magnetic disk device, the sense current supplied to the MR head is fixed to the initialized sense current value so that the reproduction characteristics of the MR head in the high-temperature operating condition are obtained and the useful life of the MR head in conformity with the desired life of the device is satisfied. Even when the MR head is operating at a room temperature or at low temperatures that are below the room temperature, the sense current supplied to the MR head is fixed to the initialized sense current value. In such a low-temperature operating condition, the sense current which is optimum to be supplied to the MR head is larger than the initialized sense current value. Hence, it is difficult for the conventional magnetic disk device to provide an adequate level of the reproduction characteristics when the MR head is in the low-temperature operating condition.
Further, the conventional magnetic disk device uses a magnetic head including the MR head, and an amount of levitation of the magnetic head from the surface of the magnetic disk becomes large when the magnetic head is operating at low temperatures. The level of the read data signal output by the MR head becomes low due to the increase of the amount of levitation in the low-temperature operating condition, and a read error rate of the conventional magnetic disk device tends to be increased when the MR head is in the low-temperature operating condition. It is difficult for the conventional magnetic disk device to provide an adequate level of the reproduction characteristics when the MR head is in the low-temperature operating condition.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved magnetic disk device in which the above-mentioned problems are eliminated.
Another object of the present invention is to provide a magnetic disk device which effectively provides an adequate level of a read data signal output by a magneto-resistive head even when the magneto-resistive head is operating at low temperatures, so that the read error rate is reduced and an assured useful life of the magneto-resistive head is satisfied.
The above-mentioned objects of the present invention are achieved by a magnetic disk device for reproducing information from a magnetic disk by using a magneto-resistive head, which comprises: a temperature detecting unit which detects an ambient temperature; and a sense current control unit which controls a sense current based on the ambient temperature detected by the temperature detecting unit, the sense current being supplied to the magneto-resistive head to detect a change of a resistance of the magneto-resistive head for the disk in a magnetic field.
In the magnetic disk device of the present invention, the sense current control unit which controls the sense current supplied to the magneto-resistive head based on the ambient temperature detected by the temperature detecting unit is provided. It is possible for the magnetic disk device of the present invention to effectively prevent the lowering of the level of the read data signal output by the magneto-resistive head when the magneto-resistive head is operating at low temperatures. A read error rate is remarkably reduced even when the magneto-resistive head is operating at low temperatures. The magnetic disk device of the present invention can satisfy an assured useful life of the magneto-resistive head and provide an adequate level of the reproduction characteristics, regardless of whether the magneto-resistive head is in a high-temperature operating condition or in a low-temperature operating condition.
REFERENCES:
patent: 5408365 (1995-04-01), Van Doorn et al.
patent: 5455717 (1995-10-01), Van Doorn et al.
patent: 5777815 (1998-07-01), Kasiraj et al.
patent: 5790334 (1998-08-01), Cunningham
patent: 5877911 (1999-03-01), Klaassen et al.
patent: 5978163 (1999-11-01), Cunningham
patent: 6104563 (2000-08-01), Dovek et al.
patent: 6118610 (2000-09-01), Handa
patent: 63-179586 (1988-07-01), None
patent: 4-86577 (1992-03-01), None
patent: 4-223285 (1992-08-01), None
patent: 5-273320 (1993-10-01), None
patent: 6-84116 (1994-03-01), None
patent: 6-162424 (1994-06-01), None
patent: 6-267008 (1994-09-01), None
patent: 7-6309 (1995-01-01), None
patent: 8-293165 (1996-11-01), None
Kiuchi Katsumi
Sugiyama Hiroshi
Davidson Dan I.
Fujitsu Limited
Greer Burns & Crain Ltd.
Hudspeth David
LandOfFree
Magnetic disk device for controlling a sense current... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic disk device for controlling a sense current..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic disk device for controlling a sense current... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2535260