Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of biasing or erasing
Reexamination Certificate
2000-12-14
2003-01-14
Faber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of biasing or erasing
C360S057000, C360S045000, C360S068000
Reexamination Certificate
active
06507448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an information recording device for recording information on a recording medium.
2. Description of the Related Art
In recent years, with the spread of computers, large amounts of information are commonly dealt, and hard disk drives (HDD) are used as one of information recording devices for recording large amounts of information. The HDD has a magnetic disk serving as a disk like medium on which information is recorded, a recording head for recording information on the magnetic disk, and a reproducing head for reproducing the information recorded on the magnetic disk.
The magnetic disk has a magnetic layer consisting of a ferromagnetic material on the surface of the disk or near the surface, and magnetic states are independently held in small regions of the magnetic layer. In operation of the HDD, the magnetic disk is rotated in the HDD at a high speed.
The recording head has a small recording coil and a pair of magnetic poles, and is normally arranged near the magnetic disk rotated at a high speed together with the reproducing head. The magnetic poles of the recording head are opposite to each other at a predetermined interval (gap length: GL) in a direction in which the tracks of the magnetic disks extend, and have a predetermined width (core width: w) corresponding to a track width in a direction of track width. When a signal current flows in the recording coil of the recording head, a magnetic field depending on the signal current is generated by the recording coil, the magnetic field leaks from one pair of magnetic poles of the recording head to the outside, and the directions of magnetization of the tracks on the surface of the magnetic disk are appropriately inverted in units of small lengths. A recording pattern of magnetization is formed by the inversion of magnetization on the tracks of the magnetic disk, and information is recorded in the form of the recording pattern.
In the HDD, in general, overwrite recording in which a new recording pattern of magnetization is overwritten on the recording pattern of previous magnetization of recorded on the magnetic disk in advance is performed.
However, in the overwrite recording, a recording magnetic field applied to tracks by a recording head is weakened by a diamagnetic field generated by previous magnetization, so that hard transition shift (HTS) in which the position of a magnetization transition point of a regional (magnetization inverted region) boundary whose direction of magnetization is inverted by a recording magnetic field is shifted occurs. Since the amount of the HTS is an amount depending on the recording pattern of the previous magnetization, it is difficult to predict the amount of shift in the position of the magnetization transition point. If HTS occurs, a reproduced waveform including the information of a recording pattern is generated by the reproducing head. However, since the peak position of the reproduced waveform is shifted, an error rate (frequency at which a read error in the direction of magnetization of a recording pattern is generated) increases.
It is known that an amount of shift is decreased by increasing the gap length GL of the recording head because the intensity of a diamagnetic field generated by previous magnetization decreases. However, when the gap length GL is increased, the recording blurred region in which a magnetic field from the recording head leaks to the outside of a track spreads. As in a conventional technique, when a track width is large, and when a recording density of information recorded on the magnetic disk is low, an error rate can be reduced by increasing the gap length GL. However, in recent years, the recording density of a magnetic disk sharply increases. When a recording density is high as described above, even though the gap length GL is simply increased to suppress the influence of HTS, an error rate still increases due to the influence of recording blur.
SUMMARY OF THE INVENTION
The present invention is made in consideration of the above circumstances, and has as its object to provide an information recording device which records information at a high recording density such that an error rate is decreased.
The first information recording device of information recording devices according to the present invention to achieve the above object, in which magnetic fields are applied to small regions of a disk-like recording medium having magnetizations in small regions on a surface to invert the directions of magnetization of the small regions so as to record information on the recording medium, including:
a magnetic head, arranged near or to be close to the recording medium, for applying magnetic fields to the small regions when the magnetic head relatively moves with respect to the recording medium to pass on the small regions of the recording medium; and
a magnetic head controller for controlling the magnetic head to cause the magnetic head to apply magnetic fields to the small regions in a free region of the recording medium in a standby state in which at least information is not recorded on the recording medium to make the directions of magnetization of the small regions uniform so as to erase the information in the predetermined free region.
Since the first information recording device of the present invention erases information in a standby state, as will be described below, adjustment of the position of a magnetization transition point such as the HTS can be efficiently performed. By the adjustment of the position of the magnetization transition point, information recording at a high recording density is performed with a small error rate.
The first information recording device of the present invention is preferably an information recording device in which the magnetic head controller controls the magnetic head to cause the magnetic head to apply magnetic fields to the small regions of the free region in which the information is erased at timings depending on the directions of the magnetic fields to record information.
When the magnetic fields are appropriately applied at the timings, as will be described in the embodiment, adjustment of the position of the magnetization transition point such as the HTS is performed.
The first information recording device of the present invention is an information recording device in which the magnetic head controller controls the magnetic head to cause the magnetic head to apply magnetic fields to the small regions at least twice to erase information in the small regions.
When the magnetic fields are applied at least twice, the information is more reliably erased.
The first information recording device of the present invention is preferably an information recording device in which the magnetic head controller controls the magnetic head to apply a magnetic field which is stronger when information is erased than when information is recorded.
When the strong magnetic field is applied, information is more preferably erased.
The first information recording device is an information recording device in which the magnetic head has a recording head for recording information, and the recording head also has a function of erasing information.
As in the first information recording device of the present invention, in the device having a function of erasing information in a standby state by a magnetic head, different magnetic heads in which recording and erasing are performed by a recording head and an erasing head, respectively need not be prepared, it is sufficient that only one magnetic head serving as a recording head and an erasing head is prepared. In this case, the device needs only a simple configuration, and is inexpensive. Positional shift (to be described later) does not occur.
The second information recording device of information recording devices according to the present invention to achieve the above object, in which magnetic fields are applied to small regions of a rotatable disk-like recording medium having magnetizations in small regions o
Nishida Syuji
Tagawa Ikuya
Uehara Yuji
Faber Alan T.
Fujitsu Limited
Greer Burns & Crain Ltd.
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