Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
1999-09-01
2001-06-05
Cao, Allen T. (Department: 2652)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
Reexamination Certificate
active
06243233
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a slider having a magnetic head and a magnetic disk apparatus with the slider, and more particularly to a slider floating up over a surface of a magnetic recording medium in an actuating time of a magnetic disk apparatus and a magnetic disk apparatus with the slider.
2. Description of the Prior Art
A magnetic disk operated according to a contact start-stop (CSS) method in which a floating type head is used has been widely adopted. In the CSS method, a slider having a magnetic head is put on a CSS region of a magnetic disk surface in a halt time of the magnetic disk apparatus, and the slider is floated up over a surface of a magnetic disk in an actuating time of the magnetic disk apparatus. In general, a reading and writing magnetic head is attached to the slider, the slider is supported by a suspension, and the slider is moved over the magnetic disk with the movement of the suspension.
The reason that the slider having the magnetic head floats up over the magnetic disk surface in the actuating time is that an air flow occurs on the magnetic disk surface when the magnetic disk is rotated. That is, the magnetic head slider floats up according to a principle of a dynamic air bearing.
In the above magnetic disk apparatus, the apparatus has been gradually downsized, and information can be recorded in the magnetic disk at a high density. Therefore, a flying height of the slider is gradually lowered. However, in cases where a flying height of the slider is lowered, there is a drawback that the slider contacts with asperities of the magnetic disk surface and is damaged. To prevent the drawback, the roughness of the magnetic disk surface is lowered to prevent the contact of the slider with the magnetic disk.
However, because a contact area between the slider and the magnetic disk in the CSS region is enlarged as the surface roughness of the magnetic disk is lowered, the slider easily adheres to the magnetic disk. In this case, there is another drawback that a motor torque required to rotate the magnetic disk is increased and the suspension supporting the magnetic head is easily damaged when the rotation of the magnetic disk is started.
To reduce the adhesion of the slider to the magnetic disk, a plurality of pads (hereinafter, also called projecting portions) are provided on an air bearing plane (hereinafter, also called a floating plane or a rail plane) of the slider facing the magnetic disk, so that the contacting area between the slider and the magnetic disk is reduced. This technique is, for example, disclosed in a Published Unexamined Japanese Patent Application No. S63-37874 (1988).
However, in cases where the pads are provided on the rail plane, the load of HGA (head-gimbal assembly) is put on the pads, so that there is another drawback that the pads are easily worn out because of the friction between the pads and the magnetic disk. Also, there is another drawback that the pads prevent the magnetic head be set to be close to the magnetic disk surface.
SUMMARY OF THE INVENTION
An object of the present invention is to provide, with due consideration to the drawbacks of such a conventional a magnetic head slider with pads and a conventional magnetic disk apparatus with the magnetic head slider, a slider having a magnetic head in which the adhesion to a magnetic disk is suppressed, the wear of the pads in a CSS (contact start stop) is suppressed and the contact with a magnetic disk in an actuating time is reliably prevented. Also, the object is to provide a magnetic disk apparatus with the slider.
In the present invention, a height of pads which are provided on a rail plane of a slider having a magnetic head is set in a range from 20 to 50 nm. In cases where the pad height is set to the range, a coefficient of the friction between the slider and the magnetic disk can be reduced to a desired value while considering a thickness of lubricant coated on the magnetic disk surface (or a magnetic recording medium surface) and a roughness of the magnetic disk surface.
Also, in cases where a pad is provided on a first rail plane placed at one side portion of the slider and another pad is provided on a second rail plane placed at another side portion of the slider, a distance from the pad provided on the first rail plane to a back end (or an air outflow end) of the first rail plane is set to differ from the distance from the pad provided on the second rail plane to an air outflow end of the second rail plane. Therefore, in cases where the slider is floated up over the magnetic disk while inclining the slider in a lateral direction perpendicular to a rotating direction of the magnetic disk, the pad of the first (or second) rail plane of which a flying height from the magnetic disk is lower than that of the second (or first) rail plane is placed on condition that the distance from the pad of the first (or second) rail plane to the air outflow end of the first (or second) rail plane is shorter than that from the pad of the second (or first) rail plane to the air outflow end of the second (or first) rail plane, so that the contact of the pad of the first (or second) rail plane with the magnetic disk surface can be prevented. In this case, to stably put the slider on the magnetic disk, it is preferred that the pad of the second (or first) rail plane of which a flying height from the magnetic disk is higher than that of the first (or second) rail plane be closer to the air outflow end of the second (or first) rail plane.
Also, when the magnetic disk is rotated at a constant speed, because a circumferential speed of the magnetic disk at a particular position becomes high as the particular position is far from a rotational center of the magnetic disk, a speed of an air flow occurring under the slider on the surface of the magnetic disk becomes high as the slider is far from the rotational center of the magnetic disk. Therefore, because a flying height of the slider at its front end (or an air inflow end) is increased as the slider is far from the rotational center of the magnetic disk, a probability that the pad of the second (or first) rail plane placed to be closer to the air outflow end of the second (or first) rail plane contacts with the magnetic disk surface is considerably reduced.
Therefore, in the present invention, the configuration of the slider is determined on condition that a flying height of one rail plane to which any magnetic head (hereinafter, called an electro-magnetic transducer) for a reading or writing operation is not attached is lowered as the slider is far from the rotational center of the magnetic disk. As an example of the configuration of the slider, a rail plane width at a portion of each rail plane near to the electro-magnetic transducer is set to be narrower than that at a portion of each rail plane far from the electro-magnetic transducer.
Also, a width of each of the pads provided on the rail planes depends on a width of each rail plane. Therefore, in cases where each pad is lengthened in the direction of a length of the rail plane to sufficiently enlarge a size of each pad, a contacting area between each pad and the magnetic disk surface is sufficiently enlarged, and the wear of the pads can be prevented.
Also, in the present invention, a value obtained by subtracting a flying height of a projection (or pad) arranged on the slider from a flying height of the electro-magnetic transducer attached to the slider is set to change from a negative value at an outer circumference of the magnetic disk to a positive value at an inner circumference of the magnetic disk. Therefore, the projection of the slider preferentially contacts with the magnetic disk at the inner circumference of the magnetic disk before the electro-magnetic transducer contacts with the magnetic disk, so that the contact of the electro-magnetic transducer with the magnetic disk can be prevented.
REFERENCES:
patent: 4757402 (1988-07-01), Mo
patent: 5768055 (1998-06-01), Tian et al.
patent: 5841608 (1998-11-01)
Kasamatsu Yoshiharu
Koishi Ryosuke
Toyoguchi Takashi
Yamamoto Takayuki
Yokohata Toru
Cao Allen T.
Fujitsu Limited
Greer Burns & Crain Ltd.
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