Dynamic magnetic information storage or retrieval – Head – Head surface structure
Reexamination Certificate
2000-06-13
2003-07-08
Heinz, A. J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head surface structure
C360S130240
Reexamination Certificate
active
06590741
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head for use in a magnetic recording/reproducing apparatus having a rotation drum and to a magnetic recording/reproducing apparatus having the magnetic head.
2. Description of Related Art
A magnetic head mounted on a rotation drum and used in a conventional technology is used in a magnetic recording/reproducing apparatus on the precondition that the head wears constantly as a magnetic tape travels. Usually, before the magnetic head is mounted on the rotation drum, its sliding face is ground by a lapping tape so as to have a shape having curvatures in the longitudinal direction (i.e., the mutual travel direction of the head and tape) and in the width direction (the direction perpendicular to the above-mentioned longitudinal direction on the sliding face) respectively.
Furthermore, a lapping magnetic tape having a large grinding capability is traveled over the magnetic head mounted on the rotation drum to obtain excellent contact with a magnetic tape. by this travel, the magnetic head is worn slightly, and the shape of its sliding face is fitted for tape travel.
In addition, since the magnetic head wears away as a magnetic tape travels for a long period and its projection amount decreases (the amount of wear is 10 &mgr;m at the gap of the magnetic head after tape travel of 1000 hours for example), the initial projection amount has been decided to have a value in consideration of the amount of wear so that sufficient head touch can be attained even if the magnetic head wears away.
The dimensions of the sliding face of the magnetic head for a VHS-format VTR are, for example, 100 &mgr;m in core width and 2 mm in length in the longitudinal direction.
As another conventional example, a magnetic head based on a reproduction principle different from that of an inductive magnetic head has been developed and put to practical use. This magnetic head is a magnetic head using a magnet-resistive effect element for reproduction (hereinafter referred to as an MR head”).
The reproduction output of the MR head is not dependent on the relative speed between the MR head and a magnetic recording medium, but is proportional to a sense current to be applied.
Recently, by utilizing this feature, the MR head has been used for digital-audio magnetic recording apparatuses, etc., wherein the relative speed between the head and the magnetic recording medium is extremely low and for magnetic recording apparatuses, such as hard disk drives, wherein recording density is extremely high and sufficient output is thus not obtained by the inductive magnetic head.
Because of the reasons mentioned below, the MR head is designed to have a minute dimension in height (hereinafter referred to as a head height) in a direction perpendicular to its face sliding over a magnetic tape. In other words, it is known that the intensity of the magnetic field from the magnetic recording medium decreases exponentially in the direction of the head height.
Therefore, in the case when the MR head is disposed over the magnetic recording medium, an inflow magnetic flux attenuates greatly at about several micrometers in the direction of the head height in the MR head. In a region into which the magnetic flux flows, the magnetization direction of the MR head is rotated by the inflow magnetic flux, and the resistance value of the MR head changes.
When a current is flown to the MR head, a voltage corresponding to the change in the resistance value generates across both ends of the MR head, and the voltage is taken out as a reproduced signal voltage for the information recorded on the medium.
In order to extend the lives of these magnetic heads, it is proposed that a protective film is formed on the sliding faces of the magnetic heads (Japanese Laid-open Patent Application No. Hei 6-119613). It is believed that if wear is suppressed by the attained
BRIEF SUMMARY OF THE INVENTION
However, in the case when the shape of the magnetic head is fitted so as to have a desired shape by making the magnetic head wear away by traveling thereon a magnetic tape having a high grinding capability, the magnetic head wears away by 1 to 2 &mgr;m for example. Therefore, the initial head projection amount and depth of the magnetic head must be determined in consideration of the amount of wear.
In addition, in the case of a small magnetic head inherently having a small initial depth, its life becomes short. Demands for solving these problems are thus present.
As described above, recently, an attempt to raise the recording density of a magnetic tape apparatus by using an MR head has begun. However, in adopting the MR head for a rotation-drum-type magnetic tape apparatus, such as a VTR, it is necessary to improve the low wear resistance of the MR head.
In the rotation-drum-type magnetic tape apparatus, the sliding area between the magnetic head and the magnetic tape is small. Therefore, the pressure applied to the magnetic head per unit area is high. In addition, since the magnetic head and the magnetic tape slide with each other at a high relative speed of more than 10 n/sec, the condition with respect to wear is severe.
Since the MR head is small in head height, it wears out in a short time, and its output is not delivered. In addition, the cross-sectional area of the MR head itself decreases with the progress of wear, and the resistance value of the MR head increases; and therefore, the MR head is broken by Joule's heat generated by a sense current supplied to detect a signal.
Furthermore, since the relationship between the intensity of the magnetic field of the MR head and the change in the resistance is nonlinear, the signal distortion due to this nonlinear characteristic is affected complicatedly by the wear. As described above, since the MR head is greatly affected by the wear, it is desirable that head touch in the initial shape of the head should be good.
Moreover, in the case when a protective film is formed on the sliding face of the magnetic head, since the shape of the sliding face cannot be fitted after the head is mounted on the rotation drum, it is difficult to obtain good contact with the magnetic tape. On the other hand, there was a problem that in case the core width at the sliding face is increased or the projection amount of the head is decreased in order to reduce the wear of the protective film, the head touch becomes worse.
An object of the present invention is to provide a magnetic head capable of obtaining good contact with a magnetic tape and being less likely to wear away and to provide a magnetic recording/reproducing apparatus using the magnetic head.
The present invention is characterized by a magnetic head mounted on a rotation drum to perform magnetic recording or reproduction by making contact with and sliding over a magnetic tape wherein two grooves substantially in the rotation direction of the drum are formed with a predetermined distance therebetween in the sliding face of the above-mentioned magnetic head making contact with the magnetic tape, and a gap is provided in the sliding face positioned between the above-mentioned two grooves.
The invention in accordance with another point of view is characterized in that constitution of the above-mentioned invention further comprises a rotation drum device having a rotation drum provided with the magnetic heads and a stationary drum adjacent to the above-mentioned rotation drum, rotation posts and slant posts for guiding the magnetic tape to the above-mentioned rotation drum device and contacting the above-mentioned magnetic tape with the external faces of the above-mentioned stationary drum and the above-mentioned rotation drum, and a capstan and a pinch roller for feeding the above-mentioned magnetic tape at a predetermined speed.
The invention in accordance with still another point of view is characterized by a magnetic head mounted on a rotation drum to perform magnetic recording or reproduction by making contact with and sliding over a magnetic tape, wherein two grooves substan
Hasegawa Hiroyuki
Hasegawa Kenji
Sawai Eisuke
Takahashi Ken
Takeda Hiromi
Akin Gump Strauss Hauer & Feld L.L.P.
Heinz A. J.
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