Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
2001-06-07
2003-02-04
Hudspeth, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S031000
Reexamination Certificate
active
06515836
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magneto-resistive effect type magnetic head that reproduces the data recorded on a magnetic tape, and to a magnetic tape apparatus that has a magneto-resistive effect type magnetic head.
2. Related Art
Hard disc drives are known as magnetic disc apparatus that record and reproduce data on and from magnetic discs. Generally, a hard disc drive has a magneto-resistive effect type magnetic head (hereinafter referred to as “MR head”). The MR head has a width smaller than the width of the recording tracks of a magnetic disc. Note that the width of the MR head is measured in the widthwise direction of the recording tracks.
As shown in
FIG. 1
, the magnetic disc incorporated in a hard disc drive has concentric recording tracks T
2
. A guard band
50
is provided between any two adjacent recording tracks T
2
. As
FIG. 1
shows, the MR head
51
provided in the hard disc drive is if SAL (Soft Adjacent Layer) type. The MR head
51
is subjected to on-track control and is thereby positioned within the width W
0
of a recording track T
2
. The data-reproducing ability of the MR head
51
is evaluated by measuring the efficiency at which the MR head
51
reproduce data from the entire width W
0
of the recording track T
2
.
It is proposed that an MR head of the type described above be applied to a magnetic tape apparatus such as a video tape recorder. The magnetic head incorporated in a magnetic tape apparatus is designed to record and record data on and from a magnetic tape, along a line inclined at a prescribed azimuth angle to the widthwise direction of the recording track of the magnetic tape. That is, the magnetic tape apparatus has a rotary head mechanism of so-called. “helical scan system,” in order to record data on, and reproduce the same from the magnetic tape.
The rotary head mechanism used in the magnetic tape apparatus comprises an inductive magnetic head (hereinafter referred to as “inductive head”), an MR head, a rotary drum, a stationary drum, and a drive motor. The inductive head is provided to record data on a magnetic tape. The MR head is used to reproduce data from the magnetic tape. The rotary drum holds the inductive head and the MR head. The stationary drum supports the rotary drum, by using an axle. The drive motor is provided to rotate the rotary drum on the axle.
The inductive head comprises a magnetic core and a coil wound around the magnetic core. The magnetic core is composed of a pair of core halves, which constitute a closed magnetic path. The magnetic core has a magnetic gap that is very narrow. The MR head has a magneto-resistive effect element (hereinafter referred to as “MR element”). The rotary drum is a bottomed hollow cylinder made of metal. The axle supports the rotary drum, at the center of the bottom thereof. The inductive head and the MR head are secured to the outer circumferential surface of the rotary drum. The stationary drum is a bottomed hollow cylinder made of metal and supports the axle, allowing the same to rotate. Hence, the stationary drum holds the rotary drum by the use of the axle.
In the magnetic tape apparatus thus constructed, the magnetic tape runs, sliding on the outer circumferential surface of the rotary drum. The inductive head records data on the recording track of the running tape, along a line inclined at a prescribed azimuth angle to the widthwise direction of the recording track. As the magnetic tape runs, the MR head reads data from the recording track of the magnetic tape.
The efficiency at which the inductive head records data on the entire width of the recording track is measured, for example, right after the above-described magnetic tape apparatus is manufactured, thereby to evaluate the data-recording ability of the inductive head and the data-reproducing ability of the MR head.
As long as no external magnetic field is applied to the MR head from the magnetic tape, the MR head is magnetized usually at 45 degrees to the direction in which a sense current flows in the MR head. When an external magnetic field is applied to the MR head while a current is flowing from one end of the MR head to the other end thereof, the ends of the MR head are magnetized at different angles. That is, the MR head can no longer have uniform data-reproducing characteristic, depending upon the direction of easy magnetization. The data-reproducing characteristic of the MR may fail to be uniform, too, unless the MR head is magnetized uniformly.
The MR head is inevitably more likely to exhibit non-uniform data-reproducing characteristic than the inductive head, depending on the position it takes in its widthwise direction that is parallel to the widthwise direction of the recording track. This fact must be taken into full consideration in evaluating the data-reproducing ability of the MR head.
The inductive head, which is incorporated in the rotary head mechanism, records data on a recording track, while writing the data over one side of the immediately adjacent track on which data has just been recorded. Thus, the azimuth angle for the recording track differs from the azimuth angle for the immediately adjacent recording track.
However, the inductive head may not be secured to the rotary drum with a sufficient positioning precision. If so, the inductive head is inevitably displaced with respect to the widthwise direction of a recording track. Consequently, adjacent recorded tracks will have different track widths W
1
, W
2
and W
3
, as is shown in FIG.
2
. In other words, the magnetic tape will have recorded tracks that differ in terms of their widths.
As shown in
FIG. 2
, the MR head
55
may not be secured to the rotary drum with a sufficient positioning precision. In this case, the MR head
55
is displaced in its widthwise direction W
2
with respect to the width W
1
of the recorded track T
3
. That is, the MR head
55
takes various positions A, B, C, D and E shown in
FIG. 2
, inevitably located off the track. If located so, the signals the MR head
55
reproduces at the positions A, B, C, D and E will differ from one another, when its data-reproducing characteristic is not uniform over the entire head width W
2
. In other words, the MR head
55
exhibits a defect that the data reproducing characteristics vary depending on each position A, B, C, D and E.
In view of the above-described problems, it is necessary to evaluate the data-reproducing characteristics (hereinafter referred to as “micro-track characteristic”) the MR head
55
exhibits at the off-track positions A, B, C, D and E which are off-tracked in the direction of the track width W
2
of the recording track T
3
. Note that the MR head
55
reproduces data from the track T
3
on which data has been azimuth-recorded by helical-scan method.
The MR head, which is incorporated in the rotary head mechanism, is displaced in the widthwise direction of a recording track when the recorded tracks vary in width. Whenever the MR head is displaced in the widthwise direction of the track, its data-reproducing characteristic changes very much.
BRIEF SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to provide a magneto-resistive effect type magnetic head that can reliably reproduce data from a magnetic tape.
Another object of the present invention is to provide a magnetic tape apparatus that can reliably reproduce data from a magnetic tape.
To attain the first-mentioned object, a magneto-resistive effect type magnetic head according to the invention comprises a magneto-resistive effect element for reproducing data recorded on a magnetic tape at a prescribed azimuth angle to the direction of width of a recording track of the magnetic tape. The magneto-resistive effect type magnetic head has a head width greater than the width of the recording track, as measured in the width direction of the recording track. The magneto-resistive effect element has a magnetism-detecting section arranged at the prescribed azimuth angle. The signal reproduced from the magnetic tape as the head is moved
Fukuda Shinichi
Ozue Tadashi
Shirai Toshio
Castro Angel
Hudspeth David
Sonnenschein Nath & Rosenthal
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